The Israelites started off as pagans. According to Biblical scholar Tim Callahan, the ancient Israelites believed in many of the gods as the Egyptians and the Canaanites.

But as time goes on, the Bible began to be reinterpreted. It is very easy when looking at the Bible to think it was all written at roughly the same time. We forget that the writing of the Bible spans approximately 1600 years. The Israelites were never a great nation, though they make claims to that in the Bible.

It is exactly this reason that the Bible was written over 1600 years, that there are so many contradictions and inaccuracies in the Bible. Now, people may object to this claim but any reader would see that it takes a certain amount of mental gymnastics and semantic hoop-jumping to make it seem like the Bible isn't contradictory or inaccurate.

But really, it's the story of a cultural transition, from ancient pagan traditions borrowed from neighboring cultures to the consolidation of those into one God.

El Elyon, translated as "Most High God", for example, was used by "Melchizedek, the Canaanite priest-king of Salem who sacrificed to him on Abraham's behalf. El was a sky god, creator and the grey-bearded patriarch of the Canaanite gods." (from Callahan's Secret Origins of the Bible).
You know the archaic image we all have of the bearded man in the clouds? That is El.

In Isaiah 14:12, it says, "How you are fallen from heaven, O Day Star, son of Dawn! How you are cut down to the ground, you who laid the nations low!"

Gary Lenaire, a former Christian musician from the band Tourniquet, wrote in his book An Infidel Maninfesto, "In Hebrew, Day Star and Dawn are Helal and Shahar. Helal and Shahar were originally Canaanite (pagan) gods, not Satan." Satan is the common reinterpretation that many Christians have today. I imagine Lenaire got this information from Callahan's book as well.

The Jewish people adopted many ancient pagan stories, including the snake tricking the woman in the garden story (Lenaire). That story predates Genesis.

Even the name the Jewish people adopted for their God Yahweh (YHWH or YWVH) was borrowed from other people. Yahweh is the unspeakable name of God, or the Tetragrammaton. Yah was one of the gods worshipped by the Arameans (Callahan), another culture neighboring the ancient Israelites. And Yahweh was originally a part of one of the Canaanite pagan pantheon and worshipped by Canaanite tribes other than the Jews (Callahan).

It makes sense that the Jews would adopt these names into their culture because the Jewish culture was a mixture of many tribes and cultures over many centuries. All the demon and angel names, the names of gods, are from Canaanite, Babylonian, Egyptian, Greek, and Persian deities (Lenaire).