1.
Back when Christianity was young, the church had to prove that they are their own religion. That they are more than simply an off-shot of Judaism. (The problem was that Judaism was older than Christianity and thus more correct.) This made it necessary to "otherize" Jews in religious terms from Christians.
2.
In the Middle-Ages, it was religiously immoral to charge fellow believers interests on loans. But that didn't count for non-believers: Jews could charge Christians interest and vice versa.
(The Muslims have a system where the bank doesn't charge you interest but gets a cut from the profit you make with that loan.)
In the Middle-Ages the first banks came up. And as Jews were capabale of asking for interest, they were able to run banks with a significant profit. Christians were not. That's how the greedy Jew stereotype came to be.
3.
Slight discrimination prevented Jews from getting a foothold in certain economic sectors: They weren't allowed to join craftsmen-guilds, they weren't allowed to buy land for running a farm...
This meant that the Jews simply moved from blue-collar-jobs to white-collar-jobs. Jews started being bankers, traders, lawyers, doctors, artists simply because nobody wanted them in other jobs.
And that bolstered the stereotypes of "otherized" Jews who don't work decent jobs and make lots of money.
4.
In early 20th Century, a misinterpretation of Darwinism became popular. Darwinism was interpreted as there being superior races and inferior races. And those "others" are of course inferior to you.
Plus, with the economic crises of the 1920s, banks became the boogeyman. And who supposedly ran the banks? Jews.
In Germany, the economic crises were spun as a jewish conspiracy to use the banks to destroy Germany. (And today the Alt-Right is back with exactly the same conspiracy-theory.)
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