Honestly need some help.

I don't no when it started exactly but after muhammad died it seemed like slavery became alot more popular for some reason, even though islam promotes the freeing of slaves. Why did it get to such an extent in which arabs would cut the privates of young boys to avoid having children and use women as their sex slaves, not treating them with the rights they deserved. Was this whole period of slavery considered wrong and against their religion, and if so, why was it so popular. I'm sorry, I've been interested in islam for awhile but this topic always trips me up.