Fear makes religion.
Fear keeps the religious religious.
Fear made monotheism (worshiping one God must offend the other Gods so we must adhere to only the most powerful God and ignore the rest).
Today, many Christians fear the alternative to heaven (burning in the fires of hell, which, according to their own bible, they will, because they supported the war in Iraq, which Revelation clearly says God commanded them not to do).
Originally, the Jewish religion was polytheistic, like the surrounding religions (and many of the Jewish beliefs seem to be derived from earlier religions).
The Christian and Muslim religions are spin-offs of the Jewish religion. That is, essentially the Christians and Muslims are some sort of Jews. This notion highly offends many of them. Many Christians, for example, insist that Christ, the founder of the Christian faith, was not Jewish. This is particularly popular in antisemitic Christian areas such as Germany.