The Catholic Church forbade usury. A Christian could not give a loan and charge interest for it. 19. You shall not lend for interest to your brother, interest of silver, interest of food, interest of anything that is loaned on interest. The Bible says that 20. You may lend on interest to a stranger, but you shall not lend on interest to your brother, so that the LORD your God may bless you in all that you set your hand to in the land where you go to possess it (Deuteronomy 23:19). Also, in the New Testament Jesus said 40. And if anyone shall sue you before the law and take your garment, give him your coat also. 41. And if anyone shall compel you to go one mile, go with him two. 42. Give to the one who asks of you; and do not turn away from the one who wishes to borrow from you (Matthew 5:42). The Bible was interpreted as barring usury against a fellow Christian.

Though there was migration before 68 AD, the failure of the Jewish Revolt and the subsequent expulsion of the Jews from the Levant, led many to migrate to Europe. As the world moved to a mercantile economy, the modern idea of a "bank arose." European Christians could not lend money with interest, and therefore Jews filled the important slot. With mercantilism, negotiable instruments arose and banks several thousand miles away from the goods being sold became key to the success of the world economy, but that's a different topic.

The trope of the "money grubbing Jew" is rooted in fact, not because Jews were greedy but because they often worked with money, especially when usury was involved. The idea has perpetuated itself since then.