The “who happened to be Jewish” is not quite the whole story. That wasn’t random or accidental. In the Middle Ages, lending money was verboten for Christians, so money-lenders were invariably Jewish.
During the middle ages through to the French revolution in many parts of Europe Jews were forbidden from lots of other occupations and guilds so lending and commerce were the only way to survive. Also, Jews tended to be literate while many others were not.