Mythically speaking, so that He could exact obedience from Man and all 'creation'.

Moses was learned in the Egyptian ways, as it's said. This meant that he was educated and socialized in a 'polytheistic' world, but this world couldn't sustain his political ambition. A monotheistic world born of polytheism could only exact strict obedience.

Am wondering,

Yes Moses was learned in Egyptian polytheistic ways, but have you considered that for the first decade or so of his life he got a different, monotheistic education? An education that polytheistic eduction and socialization and proximity to political power could not erase? Therefore I think monotheism was not born of polytheism after all.

Or how do you see it?

The assumption that lessons that were learnt in early childhood can't be unlearned isn't true. Otherwise there'd be nothing like freedom.

For example, how would one explain Mohammed's move to monotheism in a largely polytheistic world?

You should have a conversation with Ochieng of the DN. Today I would argue, he is one of the foremost authorities on Egyptian mythology - since the great Cheick Anta Diop passed away.

According to Ochieng, Moses was one and the same man as Pharaoh Akhenation.

History says Akhenaton was the inventor of monotheism in Egypt and started the worship of Aten 'the one god.'

He got into serious trouble for it. He was overthrown, his cities and temples destroyed and the worshipers of Aten scattered to the four winds.

If Ochieng is to be believed, this is how Moses/Akhenaton came to lead some of his followers (the Israelites) out of Egypt into the desert. Here their monotheistic belief system survived for thousands of years, despite being surrounded by polytheistic tribes, until the Greeks and Romans (through Christianity) and the Arabs (through Islam) made it the default belief system for much of the World.

For us, the southern dispersal of Akhenatons followers could explain why monotheism is so common among East and Southern African tribes,(compare with West Africa). It could also explain how so many ancient Egyptian words and Jewish religious rituals have found their way into the languages and traditional worship of people like the Masai, Kalenjin, Borana, Kikuyu, Chagga etc.

Philip Ochieng is just another net 'importer of religion'.

He even sports the tag 'Philip'.

No difference.