What is the theological basis for fundamentalist Mormonism's belief in polygamy?

The fundamentalist Mormons base their polygamy on Joseph Smith's Mormon polygamy.

Smith became essentially a sex addict, exactly like Tiger Woods. Some men who get power get it connected up with sex in their heads and they can't control themselves.

Smith was caught out with Fanny Alger behind the barn long before he gave the polygamy 'revelation' and got other Mormon leaders to join him in it. He claimed God told him directly that he had to do it. He was threatened repeatedly by an angel with a drawn sword and forced to do it even though he didn't want to. He said.

The real basis is the same as Muslims, for the booty!

The theological basis is rooted in their beliefs about God and aliens. In a way they are nature worshipers, idealizing sex and procreation as divine. The Bible has Holy Kings with many wives, and that may have validated their beliefs.

To really understand you have to read their story on how YHWH was a mere mortal man who transcended to god status, had a bunch of wives who gave birth to Jesus and Satan. It's all very comic book and fantastic.

The founders wanted multiple wives, especially young ones, so they made something up.

Yes, as most have said, but basic fundamentals: Hard Matter.

Man is in charge. Man wants more pussy...

But I'm going to hell for being polyandrous (woman with more than one committed male lover).

Joseph Smith, their God, made it up and he liked young girls too. This is the truth too. He was a sexual pervert and a pedophile. Read about his life

Man, they just want more pussy.

Anything else is a sad excuse.