“Since we cannot defeat Israel in war, we do this in stages. We take any and every territory that we can of Palestine and establish a sovereignty there, and we use it as a springboard to take more. When the time comes, we can get the Arab nations to join us for the final blow against Israel.” Yasser Arafat 1993.
This is the reason for the creation of the whole myth, the reason this was done had nothing to do with historical right, but at this point, these Arabs have lied about this so long they actually are starting to believe their own lie. The reason was the refusal of Middle East Muslims to allow a Jewish nation in their midst, to stop this they will go to any means, even creating a history and lying about historical claims.