One of the rare questions....that never gets asked in German history....is how Jews arrived. So this is one of those historical essays that I'll write on a certain element of history which isn't clearly laid out in most resources.
Depending on which historian you use....the Romans came into the Germanic region of central core of Europe around 58 BC (during the Gallic Wars period of six to eight years). They probably were roaming around earlier than that but this is the clear point when they established some authority over the Germanic people.
Some documents exist from around the 321AD period which identifies the Jews in the Germanic region. They came as part of the trade and commerce trend developed with the Roman trails and roads that led from Rome north into central Germany.
The chief purpose of the original crowd? Trade, agriculture, manufacture, and eventually they got into the lending practice.
The chief trading points of the Roman Empire in this early period? Mainz, Speyer and Worms. You can pull out any map of the region.....it all leads along the Rhine River.
Because of various rules established by the Catholic Church after the Roman Empire dissolved....the Jews were on the 'approved list' of money-lenders. A key word that you might see thrown around occasionally is "Usury"....which basically means the black-market side of loaning money. If someone was dealing loans under this Usury-umbrella....it tends to mean a dishonest or unethical type of loan.....maybe an unfair interest rate.....or the requirement of a hefty amount of property should the loan fail.
It's safe to say that as the loan-handlers of the time.....people had an appreciation of their services but also hated dealing with them. If you needed money to solve a problem.....you usually had very few choices beyond the Jewish loan merchant in your local area. So in some ways....this was the beginning of a negative perception about Jews.
If you go back to the era of 1096 to 1349....it's a pretty negative period for most Jews in central Europe. Between Koln, Speyer, Mainz and Worms....roughly 12,000 Jews were murdered over one short summer (1096). Anger over the money business? Yeah, it might lead back to that as one of a couple of reasons for the attitude by the locals..
Trade and commerce occurring in this seven-hundred year period without the Jews? Maybe, but to a much lesser degree. You have to remember that the ability to loan and concentrate great deals.....was fairly dependent on cash flow. If the money wasn't there.....big deals would not occur. Course, this also involved risk, and if you failed to pay loan off.....it meant a fairly big loss to your lifestyle and comfort (maybe losing your bakery, your farm, or livestock). This loss would unsettle most people and set up revenge perceptions down the line.
So, in simple terms.....without the Roman invasion of central Europe and decades of occupation.....you wouldn't have had much reason for the Jewish merchants to arrive and set up shop.