The Zionists were running the show. Surely you've heard of the Zionist Organization?

Arabs and Palestinians intermarried freely. Zionists were segregationists.* See https://comrademorlock.medium.com/did-zionists-start-every-violent-clash-in-palestine-between-1882-and-1930-05daa6e9a9a9

*The Ashkenazi, however, had intermarried freely with Europeans, which is why they're best described as Europeans. See https://www.livescience.com/40247-ashkenazi-jews-have-european-genes.html