I strongly, strongly suggest you revisit some of the preconceptions that led you here. I was going to instinctually retort, but instead took 5 minutes to read the relevant Wikipedia article on the topic: https://en.m.wikipedia.org/wiki/Slavery_in_Africa#West_Africa. It is clear that the topic is more nuanced than I originally thought, so thank you for bringing that to my attention, but it's a crude and broad brush to imply that most slaves already existed in slavery prior to the Atlantic trade. There is also a significant difference between slaves in Africa who were exchanged between local groups in a wholly African context, versus slaves chained up and flung across the Atlantic with a 12% mortality rate and forced under a European slavery conception.

I suspect your response has rubbed others the wrong way, as it did myself, so consider this an attempt to find a common ground for dialogue - whatever the history of Africs prior to the Atlantic Slave Trade, I think we can agree that what happened was utterly grotesque and an atrocity upon the history of our common humanity.