>God wanted the sons of Adam to build civilization and be chaste
I'm not so sure about this since the first city and civilised arts were founded by Cain and his family, and ever since cities have done much to cultivate and incubate some of the worst atrocities against Divine Law, from Sodom to San Francisco.
As for polytheism, it was pretty much just misguided man trying to find divinity in just about everything other than Divinity Itself, so they started worshiping seasons, stars, clouds etc. It's from this kind of monotheistic animism that anthropomorphised polytheism emerged, and not all at once, either.