They were managing the money, not just taking it. But I wouldn't expect a smooth brain like yourself to understand that.
Discussion
They were not "forced".
Bavaria was part of the Carolingian empire. Usury had already been banned in 806 and in 814 Charlemagne got really specific:
"Let no Jew presume to have a money-changer's table in his house"
https://origin.web.fordham.edu/halsall/source/814capitul-jews.asp
This predates the church law in 1311 that was directed at Catholics.
The following chapter from The Oxford handbook of the economics of religion explains Jewish self selection into finance in detail
https://www.tau.ac.il/~eckstein/pdf/Botticini%20and%20Eckstein%20Handbook%20Chapter.pdf
The Hebrew bible also bans usury of course, except it's ok to do it to Gentiles because of our supposed moral failings.