I think it’s mostly about power. Sexual satisfaction is probably a part of it, but power seems to me to be a far simpler explanation. The same reason you recruit soldiers when they are young. Easier to make yourself the authority, and gain the power to direct their lives.
Tris
Burundi I don’t have time to go through the link here, but, after searching, seemed to be dealing with polygamy, teen marriage, and the Mormon Church at a better level than all the news links lately.
The parentsource is here. looks like a lot of decent info there. Hope it helps. Again, I’m posting sans time to elaborate, and hope you can.
It’s a Mormon site, but looks like it’s well-thought and large on explaination of the main sect.