It's all about the banking. Medevial church laws basically prohibited christians from making loans with interest, so the Jewish people were the only ones who could, and they got rich off it, and then everyone got pissed off.
Then families like the Rothchild's started owning everything and funding wars, often both sides.
http://en.wikipedia.org/wiki/Rothsch...iracy_theories
Even the Vatican is pushing this now:
http://www.reuters.com/article/2011/...45887020111024