I can partially explain how the money-grubbing stereotype arose. My main source is James Mitchner books.

In most of Europe Jews were not permitted to own land, so they were not employed at farming like 90% of the population. Usually most lucrative commodities markets (salt, beer, etc) were monopolized by a king or local noble, so they were excluded from those. Anti-semetic nobles and bishops often forbade them from practicing other trades as well. Most Jews in Europe were poor ghetto dwellers. Somehow they maintained their cohesion and tradition, and those few who prospered economically had to find innovative ways to do it.

For most of the middle ages the Catholic church was opposed to usury. On occasion they banned usury altogether, but the need for a credit system was strong enough that they adopted a work around. Bishops decided that it was sinful (read illegal) for a Christian to charge interest on another christian. But, Jewish people were exempted from these statutes.