What was the Jewish conspiracy theory?

Answer 1

There have been quite a few, but the general theme is that there exists an international Jewish syndicate (of which most/all Jews are presumably members in some capacity) whose goal is to completely control the world's finances and political arena, force the races of the world to mix, and install (depending on which lunatic you ask) either global communism or global serfdom for non-Jews.

Answer 2

There have been a number of conspiracy theories about the Jewish peoples. Several of the most common are that Jews control the world economy, and that the Jewish started the Holocaust in order to justify the creation of Israel.