I mean, Jews were legally barred from most professions in much of Europe. If you can’t be an artisan, a retainer, or a peasant farmer, not sure how many more viable options there are for making a Medieval living.
So, you ban a group of people from most professions. You exclusively allow them to work in another profession. And, it’s a group of people that share a religion, so they intermarry and attend religious services together.
It’s a real mystery why so many of them work in the same profession, isn’t it!
Incidentally, this also explains why there are so many jews in Hollywood. Being a populist entertainer (like vaudeville) was one of the careers you could pursue as a jew in the late 1800s / early 1900s. When radio and movies first started, there were no incumbents who could refuse to allow jews into the business. Hollywood itself existed because it was a way to try to get out of the range of people trying to enforce Thomas Edison’s patents. I’d imagine it wasn’t just Edison’s patents that they got away from, but all the existing power structures that kept jews out of jobs.