Christianity and Islam were the two biggest religions (Judaism was third) in medival Europe. The Christians saw the Jews as sinners because "they killed Jesus" and the Islamics as infidels who worshiped a false god. Islam was actually theonly peaceful religion... until they cast the Christians out of the holy land. This started the Crusades, which boosted both religion's honor, since anyone who died in the crusades went to heaven.
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They weren't originated in Europe. They spread there from the middle-east. Trade between regions, as well as wars of conquest, were largely responsible for the dispersal of both people and culture.
Islam and Christianity both trace their roots to Judaism. All three are, in fact, merely different branches of the same monotheistic religion.