Jews once earned their living from farming and handicrafts. But they were forced out of landowning in Europe by the Catholic Church, which collected ecclesiastical tithes on land holdings, and which might no longer be paid if land fell into Jewish hands. The craft guilds that arose in the later Middle Ages shut Jews out by exclusionary policies.
As Jewish settlements became insecure by their dependence upon the toleration of the Christian monarchs and nobles in power, Jews gravitated to movable property, especially precious gems and metals which could be readily concealed, transported, and trafficked.
This dynamic engendered contempt for Jews among western Christendom, as commerce became closely connected with Jews, who were regarded as avaricious.
Odious to conservative Christians, Jews nonetheless became indispensable to the political authorities. Besides borrowing money to the powers that be, Jews were often employed as indirect tax collectors.