because they wanted to
This is the place where Abraham was going to sacrifice Isaac making the area very holy.
Answer 1They are two 'mounts' next to each other.Mt Zion was a Jebusite stronghold captured by David (1Kings 8:1; 1Chronicles 11:5) (2Samuel 5:6, 7, 9) which became his royal residence (Psalm 2:6). When the Ark of the Covenant was transferred there it became especially holy to God. (2Samuel 6:17).Mt Moriah was north of Zion, where the Temple was built during Solomon's reign. Eventually the term "Holy Mountain" and "ZION" came to refer to the combined area of Zion and Moriah, Jerusalem itself.(Isaiah 66:20).[Comment moved to Discussion Section.]Answer 2Yes and No.Historically, Mount Zion was used interchangeably with Mount Moriah. Both referred to the Temple Mount/Foundation Stone where the Dome of the Rock Shrine currently sits. It is in this location that the Jebusites had their fortress, David had his palace in close proximity, and Solomon built the Temple.About 2000 years ago, Judeans started referring to a second mountain, to the southwest of the Temple Mount as Mount Zion. This mountain is currently located to the south of the Armenian Quarter and is still called Mount Zion. They stopped using the term "Mount Zion" to refer to the Temple Mount and instead used Mount Moriah to exclusively refer to that.
Because it is part of the structure of the Temple Mount which housed the Holy Temple.
The two Holy Temples are believed to have been built on the Temple Mount where the Dome of the Rock currently stands.
The "western wall" of the Temple Mount, also known as the "wailing wall", in Jerusalem, is probably the most holy site for the Jewish people. It is the exposed surviving wall of the Temple that stood most recently until +/- 70 C.E. (A.D.) when it was destroyed by the Romans. Jews from around the world come to this location to pray, and to leave written prayers stuck in between the stones. It is called the "wailing wall" because it is a place of lamentation and anguish over that destruction. The Temple Mount itself is important, perhaps equally so, because it sits on top of Mount Moriah, the historical site where Abraham was said to have sacrificed a ram instead of his son Issac, thus departing from prior cults of human/child sacrifices to animal sacrifices. Because of its relationship to Abraham, it is thus also a holy site for Christians and Muslims alike. The only house of worship on the Temple Mount today is the Al-Aqsa Mosque, which houses the Dome of the Rock, which is that rocky outcropping of Mount Moriah that lays intentionally exposed to view.
Today the temple of Solomon is not there but in its place a mosque is standing.
The Temple on the Mount
The Temple Mount, or Har Habayis, where the Beis HaMikdash stood.
This is where Abraham brought his only son Isaac and was prepared to sacrfice him just like the Lord had asked him but right before he was ready to kill him an angel said "stop God sees how faithful you are"
According to Judaism it is the holiest place on earth: the place where the Holy Temple stood (the Temple's lower rows of stones are still visible there) and God's presence dwelt.
Bethlehem, Calvary and Jerusalem are holy to Christians. The temple mount which is the base where the temple of Solomon used to stand is holy to Jewish people and for some reason the same spot is called holy by muslims because muslims built a mosque where the temple of Solomon used to be.
That would be Mount Moriah (Genesis 22 'MowreeYah'), later to become the site in Jerusalem where King Solomon had the first Temple built. This was destroyed just before the Babylonian Captivity circa 586 BC, then rebuilt in the days of Ezra, Zerubbabel, and Nehemiah. Additionally, just before the time of Messiah, King Herod made significant additions, and it became known as 'Herod's Temple.' Messiah prophesied the destruction of this and also of Jerusalem (Matthew 24, Mark 13, Luke 21), which occurred at the hands of the Roman army in 70 AD. Muslims believe that Muhammed ascended to heaven from this same place. Presently this site-- known as Temple Mount-- is in Old City Jerusalem, where stands the Dome of the Rock. It is clearly visible from atop the Mount of Olives.