That is an excellent question. There are many answers.
The short answer is that the Romans were masters of cultural amalgamation through manipulation of religious politics: essentially, they went around saying hey, all those gods you worship? Same as ours but with different names. And since our emperor is the high priest of all of them, that would make us a divine authority and your political masters. Now join our empire or die. The Jews presented a huge problem to the Romans: they were monotheistic, and the Roman political machine couldn't deal. In the end, the Romans eventually came to embrace a radical cultural shift in religious practices and embraced a derivative of Judaism as a monotheistic state religion out of Rome, and that became Christianity - but to the Jews, the damage had been done, expelled from Judea and made to live as traders and merchants wherever they could.
Things changed after the Mongolian invasions of Hungary and Poland where central Europe was in desperate need of heavy fortifications against the genocidal war machine of the Khanate. Europe could have fallen to the Golden Horde so easily but the European kings offered a deal: anyone who invested in fortified infrastructure would be offered generous land deals, and since there was a passage of the Bible that was interpreted to mean that Christians couldn't lend money, that meant Jewish merchants. The Jewish population of Europe grew sizeably, and it was during this time that the false association of Jewish elite with finance started to originate.
Hundreds of years later, the threat outside Europe faded and what was left was the domination of Austria in central Europe. Dissasociated from the reasons why so many so much land had been given to Jewish communities, and constantly in need of money because Austria was basically always at war, allegations and conspiracy theories on wealthy Jewish families - some of whose descendents experience targeted harassment of conspiracy theorists to this day - can be directly traced to the Austro-Hungarian empire from the 1600s to the 1800s, with the intention of seizeing up land and wealth for the state. As Poland eventually became swallowed by Prussia, Russia, and Austria, the European Jews were stripped of their wealth and kept in a position of submission in order to suppress any notion of independence.
Harassment against the Jews became a constant state-sponsored presence from there, escalating to mass migration and the holocaust.
Caption this Meme
