Its a history question.
It goes way back in time to Esau and Jacob.
Actually it was Abraham who was the one to blame.
HE drove off HIS SON Esau into the wilderness with his mother whom Abraham was screwing and kept his first son Isaac whom he had with his WIFE instead of her helper.
So we have Abraham to thank for the conflict between these peoples. Esau was the head of the Arab world and Jacob became the head of the Jewish people.
There has been conflict between them ever since.
in short, this is what happens when ya screw around outside of the one you are married to.
And then throw away the mother and the son YOU created.
Yep, Abe didn't do the world any favors with that mistake.