The Holocaust was not a stand-alone event in the history of anti-Semitism in Europe. A lot of European anti-Semitism was derived from previous Christian fundamentalist tropes, such as that the Jews killed Jesus or that they killed Christian children and drank their blood for the evulz. What made the Holocaust different from many previous anti-Semitic atrocities was that it was also partially "justified" through racist anthropological explanations of why Jews were supposedly evil and/or inferior. So both religious fundamentalist and pseudoscientific justifications had equal parts in the Holocaust.
Again, the jury is still out on Adolf Hitler's religious views. I highly doubt that he was an atheist, as many fundies claim, but I doubt his religious claims were anything more than political pandering either. He faced some opposition from German churches because of his policies that forced kids to join Hitler Youth (which was conveniently scheduled so as to intrude upon other church holidays) and because of the Nazis' relative tolerance of extramarital relations (as long as they resulted in more "Aryan" children to die for the Reich).
I don't believe, however, that European anti-Semitism is solely the result of Christianity. IIRC, Christianity never targeted Rroma the same way they targeted Jews, but bigotry against them persists regardless.
