No independent Arab or Palestinian state ever existed in Palestine. They may have lived there longer and been always there but they were never a real country. But when the Israelis came back and the land was given to them they had a real country unlike the Palestinians.

The territory was captured in defensive wars. Even after the land was given to them, they successfully defended the land by winning several wars. Even if they say that the land is there the jews beat them multiple times in war and won the land for themselves so the land is technically theirs.

The international community granted the Jewish people the land in 1948. United Nations including the U.S. gave land in Palestine to Israel. The united nations including multiple countries like the U.S. and others gave the land to the Jewish people so in a way the whole united nations say that the land belongs to the Jewish people.