I'd argue that the source of virtually all antisemitism isn't left-wing or right-wing philosophy, but populism.
I'm clearly talking modern era, not deep-historic, but even much of the antisemitism during the Medieval/Renaissance period was populist, yes. Every time a crisis emerged like a plague or a famine that could take down a royal family, blaming it on the Jews was an effective way to harness populist rage.
Established religions were antisemitic in function, of course, but it was more about consolidating power than targeting Jews specifically.
