Cry havoc, and let slip the dogs of war!
(media.scored.co)
Jews never made up more than 1-5% of the population of Europe and were politically insecure by papal decrees that stripped them of any ability to own property or have positions of authority or power. Sure, they were given the power (by the pope) to lend money because Christians have usury restrictions (as do Jews, but Jews make exemptions if lending to non-Jews), but it sounds like you're ascribing European wars between various lords and royal families by an extremely small population of people. Which by the way, if was true, then that's pretty impressive that such a disadvantaged and insecure people could sway the head of kings to manipulate wars.