The way the question is written is to assume that it is not theirs, which is not the case in the slightest. According to historical, religious, legal, and political grounds, the territory of the British Mandate of Palestine at least partially, if not entirely, belongs to the Jewish people.
1) Historically: The Jews have an undeniable presence in the land from at least 700 BCE until 70 CE and this is proven not only by the Biblical account, but from Assyrian Ruins, Babylonian documents, Hellenistic inscriptions, and Roman volumes. Jews had a continuous presence in the land from 70 CE until the present day (even though they were nowhere near the majority) even though they were forcibly deported from the territory. The fact that they survived, as opposed to the Arameans or Hittites who were similarly exiled does not illegitimate their claims.
In addition to the population-part of the historical claim, Jews have physical ruins and cities that are very sacred to them in the territory of the British Mandate of Palestine. The city of Jerusalem is mentioned over 700 times in the Jewish Bible. The city of Nablus used to be the Northern Metropolis of Shechem. Hebron was the first capital of Ancient Israel whence Saul ruled and David ruled until he conquered Jerusalem from the Jebusites. Even more recent sites like Masada document the Jewish presence and struggle to persevere.
2) Religiously: The Jewish claim to have a connection to the land of the British Mandate of Palestine is firmly grounded in their religion. Jews as early as the Babylonian exiles wrote about returning to the land because God had promised it to them. According to the Pentateuch, God promised Abraham that piece of land. (This promise is even acknowledged in the Qur'an 5:20-21, 17:104, and 26:59.) Many Jewish Holy Sites are in Israel such as the Kotel Hama'aravi (Western Wall).
3) Legally: By international law, the Ottoman Empire took the territory from the Seljuks and Abbassids by internationally recognized conquest. The territory was ceded to the British as a Mandate by the Ottomans as a term of surrender in World War I. (Even though the British had promised the territory to both the Arabs and Jews during the War, neither promise is legally binding.) According to the terms of the Mandate, even though the British were in control, the League of Nations had official jurisdiction. In 1947, the British gave direct authority to the League of Nations' successor, the United Nations, in accordance with the terms of their Mandate. The UN passed the 1947 Partition Plan that gave both a Jewish State and an Arab State the Right to Declare Statehood. The fact that the Arabs decided not to immediately declare such a state does not make the Israeli declaration any less valid. (It is important to note that Palestine did declare statehood on these grounds in 1988, which further cements the legality of this view.)
4) Politically: Jews invested a lot in building the political and physical infrastructure of the land even before they had control. Jews built farms, trained military brigades, created political parties, studied government, and defended themselves. This created a system that was able to repel the Arab Attacks in the Arab-Israeli War of 1948-9, secure expanded borders in the Six Day War of 1967, and hold those borders in the Arab-Israeli War of 1973. Israelis were actually able to exert control over this territory.
Of course, this list is not exhaustive, but should capture the sentiment of the question.
According to historical, religious, legal, and political grounds, the territory of the British Mandate of Palestine at least partially, if not entirely, belongs to the Jewish people.
1) Historically: The Jews have an undeniable presence in the land from at least 700 BCE until 70 CE and this is proven not only by the Biblical account, but from Assyrian Ruins, Babylonian documents, Hellenistic inscriptions, and Roman volumes. Jews had a continuous presence in the land from 70 CE until the present day (even though they were nowhere near the majority) even though they were forcibly deported from the territory. The fact that they survived, as opposed to the Arameans or Hittites who were similarly exiled does not illegitimate their claims.
In addition to the population-part of the historical claim, Jews have physical ruins and cities that are very sacred to them in the territory of the British Mandate of Palestine. The city of Jerusalem is mentioned over 700 times in the Jewish Bible. The city of Nablus used to be the Northern Metropolis of Shechem. Hebron was the first capital of Ancient Israel whence Saul ruled and David ruled until he conquered Jerusalem from the Jebusites. Even more recent sites like Masada document the Jewish presence and struggle to persevere.
2) Religiously: The Jewish claim to have a connection to the land of the British Mandate of Palestine is firmly grounded in their religion. Jews as early as the Babylonian exiles wrote about returning to the land because God had promised it to them. According to the Pentateuch, God promised Abraham that piece of land. (This promise is even acknowledged in the Qur'an 5:20-21, 17:104, and 26:59.) Many Jewish Holy Sites are in Israel such as the Kotel Hama'aravi (Western Wall).
3) Legally: By international law, the Ottoman Empire took the territory from the Seljuks and Abbassids by internationally recognized conquest. The territory was ceded to the British as a Mandate by the Ottomans as a term of surrender in World War I. (Even though the British had promised the territory to both the Arabs and Jews during the War, neither promise is legally binding.) According to the terms of the Mandate, even though the British were in control, the League of Nations had official jurisdiction. In 1947, the British gave direct authority to the League of Nations' successor, the United Nations, in accordance with the terms of their Mandate. The UN passed the 1947 Partition Plan that gave both a Jewish State and an Arab State the Right to Declare Statehood. The fact that the Arabs decided not to immediately declare such a state does not make the Israeli declaration any less valid. (It is important to note that Palestine did declare statehood on these grounds in 1988, which further cements the legality of this view.)
4) Politically: Jews invested a lot in building the political and physical infrastructure of the land even before they had control. Jews built farms, trained military brigades, created political parties, studied government, and defended themselves. This created a system that was able to repel the Arab Attacks in the Arab-Israeli War of 1948-9, secure expanded borders in the Six Day War of 1967, and hold those borders in the Arab-Israeli War of 1973. Israelis were actually able to exert control over this territory.
Of course, this list is not exhaustive, but should capture the sentiment of the question.
There are several reasons why people in various nations around the world felt that they should support a Jewish State in Mandatory Palestine, even if they were not Jewish themselves.
1) The Promises: (written by other people)
View 1: When the British first occupied the area it was Palestine, but before they left the promised it to the Jewish population, thus Israel was formed. The British made two separate promises (one to the Arabs and one to the Jews), but the latter one was followed through one.
View 2: Those promises were made in 1917 during World War 1, and until 1948 the area was under British rule. From the outset there was conflict in the area between Jews and Arabs, and it became increasingly intense in the 1930s with the persecution of the Jews in Nazi Germany. In 1948 Britain's mandate (authority) to rule the area expired and the United Nations resolved to split the area into two states.
View 3: After WW2, Britain and other European powers made lots of promises. The Holocaust was a main reason for the Zionist movement to create a jewish homeland. Britain handed this case over to the United Nations to handle. They annexed a small part of Palestine for the Jews.
2) Be Gone & Good Riddance: (written by someone else) Many nations looked on with favor and relief, assuming that all Jews would eventually migrate there, and the nations would finally be rid of them. But even that fond hope was not enough for most Muslim nations, who bitterly opposed the creation of Israel, and after 64 years, still do.
3) Holocaust Pity: The Holocaust bore out two major truths as concerned the Jewish people. The first was that without a government loyal to their interests, they could easily be targeted against and brutally murdered. The second major truth was that such an event was no longer a hypothetical since 6 million Jews were intentionally mass-murdered by what had previously been seen as one of the most progressive modern countries: Germany.
4) Middle East Control: Although it seems odd to say it today, both the United States and the Soviet Union believed that Israel could be converted to "their side" in the Cold War. Given that any Jewish State in the Arab World would be isolated, it would be natural for such a state to create a strategic relationship with one of the major powers. Additionally, a Jewish State might be able to influence neighboring Arab states and make them more pliant as concerns oil shipments. Both the USA and USSR supported the Creation of the State of Israel for these strategic reasons.
5) Solidarity with the Oppressed: Many nations in Latin America supported Israel because they sympathized with the oppressed Jewish people and saw the Independence of Israel as akin to their wars against Spain/Portugal and the internal fights for more indigenous equality.
6) Because It's the Right Thing to Do: There was certainly support for a Jewish State because some just saw it as the proper thing to return Palestine to the Jews. Churchill, who was no longer Prime Minister, held many pro-Zionist views out of respect for the Jews and their contribution to that region of the world.
7) Diplomatic Pressure: Both the United States and Soviet Union pressured their allies and third world countries to support the United Nations Resolution. This does not make the vote any less valid, but is worth noting.
See also the Related Links.Link: Jewish history in Israel
Nobody put the Jews in Palestine. They chose to go there. Historically it was their homeland and they returned in fulfillment of their dream to return.
People are not required to "deserve" an inheritance; it was given.
They don't. They think they should have the land of Israel, because they have a connection to the land that goes back 4000 years.
The entire Tanakh (especially verses such as Genesis 28:13, Deuteronomy 1:8, and many similar verses), together with the historical fact of their having lived there for many centuries.
The Exile of Jews from palestine is known as the Diaspora
Because Palestine keeps attacking the Jews.
no
No. Jews had already been migrating to Israel/Palestine in substantial numbers since 1919.
There have always been Jews in Palestine. They were not the majority between the years 132 CE and 1949 CE.
The declaration gave the Jews of Palestine the hope that they might one-day have a country of their own.
Diaspora.
no
Sanhedrin
they had part of palestine.
The Muslims and Jews both claim that Palestine is their land at that they have been living there for thousands of years. The Muslims do not have any proof of their claim, but the Jews do.
No. For most of the last 2,000 years, the Jews in Palestine were a repressed minority (or on occasion a repressed majority). Probably the most bloody period for Jews in Palestine was during the Crusades when Christian leaders slaughtered numerous Jews, especially in Jerusalem. However, Jews suffered other calamities in Palestine, such as the destruction of both Great Temples and the exile of significant portions of the Jewish population.