Why did European Jews begin migrating to Palestine in the 1800's?

Answer 1

During the late 1800's there was a strong movement to return to the "promised land" of the Old Testament, called Zionism. As this movement gained popularity, large numbers of Jews from around the world resettled in what would become the British Mandate of Palestine.

Herzl explained quite well that the European concept of a nation-state was dependent on the idea that all of the people in any particular nation were of the same ethnic stock and heritage. Jews were branded by this system to be "the Other" and were regarded at best as possible equals and at worse as traitors, spies, thieves, and fifth columns. When the Dreyfus Affair turned out marches in Paris that said "Death to the Jews" on account of a kangaroo court against a particular guiltless Jew, it became clear that the Jew could not be integrated into Europe.

Ahad Ha'am explained that the Jewish Soul is intrinsically connected to his history and in the same way that a German-American can never be as properly German as a German in Germany, the People of Israel can never be as properly Jewish if they are not in the Land of Israel. The relics in that land speak to a Jewish sensibility and character. There are also religious reasons as expounded by Rav Avraham Kook which posit that the development of a Jewish State in Israel hastens the arrival of the Messiah.

Answer 2

Actually, there has always been a Jewish presence in the region of the world currently known as Israel, Jordon, Syria, Lebanon, etc. For example, the communities of Hebron and Tsfat have had sizable Jewish populations for over 2000 years.

In the waning years of the Ottoman Empire, during the late 1800's (not the early 1900's), the strip of land currently known as Israel was largely uninhabited. Those who did live there did not actually own the property they lived on, for the most part, as it belonged to the Empire itself. And the Empire was running out of money.....so it invited European Jews to come settle, to make capital improvements, and (most crucially) to make monetary investments in the region.

So in the 1880, European Jews began agricultural and economic development of the area. And, according to census documents, this was followed by an influx of Arab immigrants from Iraq, Eqypt, and other outlying areas.
During the early 1900's there was a strong movement to return to the "promised land" of the Old Testament, called Zionism. As this movement gained popularity, large numbers of Jews from around the world resettled in this area.