I really do not see early antisemitism as modern antisemitism. I see it more as a primitive tribal response to a declared tribe in almost every large community. All minority tribes were then vulnerable to communal attack as we see even today in India and elsewhere.
Antisemitism arose with modernism where a philosophical rationale other than tribalism became necessary to rationalize the irrational.
What made the Jewish experience unique was their concentration on commerce which was necessarily a minority position in every community. A little like the one chinese restaurant and one Jewish store in every town in the prairies and no other restaurant or merchant around. These were not on the edge of society either but in the foreground allowing an easy focus for bloodlust when things went bad.
The First Victims of the First Crusade