Regarding the jobs that Jews were allowed to have in Europe for centuries, I'd like to add that it wasn't only money lending, which in fact was practiced by some. The vast majority of Jews took different trades to survive. Some were indeed traders, buying and selling merchandise, but some were also goldsmiths, jewelers, carpenters, blacksmiths and so on. Rabbi Eliezer aka "Baal Shem Tov", the founder of the Hasidim, was himself a shoe maker and was very poor.
Also, most of the time and in most countries Jews weren't allowed to own land, so that also put severe limits to what they could do.
One last comment as the Jews being seen as rich. Clearly some of them were if not rich, better off but that still was relative.
You see, on top of paying regular taxes to the city, the duchy or the kingdom or all of them, there were special taxes that Jews had to pay. Sometimes they had to pay a fee to go in and out of the Jewish section of town, or ghetto.
Periodically, the government or the Church or both would stage some incident that involved Jews; riots against them followed with loss of life and property. Then, the Jews would be forced to gather in a synagogue or other place while the authorities searched the houses for you-name-it. This was just blackmail to take money away from them. Some communities didn't have the amounts of money that were required of them, and they were kicked out, their property confiscated and again, with loss of life, raped women and children, etc.
So it wasn't that the Jews in general were rich, as a matter of fact the vast majority lived in extreme poverty, even by the day's standards. And sure enough, there were some that were rich and a few made it to be the "court Jew". Shafirov I think was one of those, converted to Orthodoxy and founded the secret police in the time of Tsar Peter I (please correct me if I'm wrong).
It is amazing how this has affected the lives of some of us, even today.