In the original mythology, things got a little bit complex. First and foremost because it was outright stated that like all angels, satan had no free will. When he rebelled, it wasn't his choice to do so. It was so the pantheon that Yahweh was a member of at the time could flex on having their servants beat up another group of servants who couldn't fight back. And yes, the original Hebrew religion was polytheistic just like most other religions of that era and region. It didn't get squashed down into a monotheism until one of the later Hebrew Kings marched into the temple and destroyed the statues of all the other gods except Yahweh. But the point is, that from the start the whole rebellion thing was staged because the gods needed a villain.