Long before the world even heard of the United States, slavery was ongoing and VERY lucrative to slave trading individuals and governments.
None of it could have taken place at all without the eager and voluntary participation of African natives themselves.
Without good maps (any maps), considering the diseases, terrain, weather, brutal inter-tribal warfare, language barriers and everything else, no one would have even considered ‘slaving’ as an enterprise. All these obstacles were mitigated by African native tribal chiefs and others who knew the continent and could perpetually deliver masses of their own brethren to coastal ports for export.
Yes...it was very lucrative for THEM and for Europeans and others who engaged in slave trading.
One of the important steps that seem to be left out of any discussion with libs on the subject. They prefer the story about how all white armies invaded the dark continent and captured all those slaves.
For many centuries, the North Africans made their summer raids to the south coast of France to round up a crop of slaves. The same thing happened in what is now Ukraine, with the Turks making their summer raids to round up a crop of slaves. It goes without saying that the slave traders were moslems, and the slaves were white. Mostly young white females. This is one reason why the Russians still hate the Turks. They have long memories.