Ah yes I learned it in islamic histories. though all of that slavery were happen when islam still in process of development (The Prophet Mohammed still spreading his words and fighting againts kafir quraisy) in the end of the day the prophet freeing all of them. The Qur’an does not explicitly condemn slavery or attempt to abolish it. Nonetheless, it does provide a number of regulations designed to ameliorate the situation of slaves. It recommends freeing slaves, especially “believing” slaves. And that is because as I said above, the verse was when islam still in development. But nonetheless the slavery was still continouing during war period till it was abolished and being forbid in the modern day. Well not every people loyal to their own religion.
I suggest if you really want to research about it ask an ulama or someone more knowing in this. You sure are trying to find a fault in my words or statement which makes my head hurt just to defend my own religion to not being misused :(