Since so much of the literate, conscious slave trade comes from societies of Central Asia (apparently also elements of Sweden and England, and of course the Portugese).. I was curious and asked an observant Muslim here about slavery.. he just looked calmly and replied "it was time for it to end" .. I got the feeling that the Muslim world had some kind of internal reckoning, and did (mostly) end the slavery trade at a certain time, similar time frame to the Civil War.
From the outside, not a specialist here.. it seems like the remaining modern slave trade is mostly driven by raw commerce.. like the fishing boats for example.. Zooming out, it seems like selling known-addictive drugs has similar drives..
In fact, it was one of the drivers of the Crusades, an idea conveniently forgotten by Muslims who point at the Crusades as evidence of the West's hostility to Muslims.
Enslaving others is, while not necessarily normal, not uncommon. The enlightenment really changed things around, which shows the power of ideas.
I'm sure Al Jazeera has a documentary.
what is not clear about that question mark?