If you check into the history of Africa, you will find that the slavery over there among the Arabs and various black tribes was hell, compared with the heaven that black slaves came to in America. Sure, there were a few bad slave holders in America. But you don't mistreat your slaves if you want them working hard for you. Rather, you incentivize them. And that is what the vast majority of the slave holders in America did.
Slaves were extremely expensive in the U.S., and the percentage of people who owned them was low. On top of that, anyone could own slaves in the U.S., including well-off black people, and that did happen although I believe that it was pretty rare. At least half of my lilly-white family came to the U.S. long after slavery was abolished, and long after most of the African stock was already there.
Interestingly, Judaism recognizes superiority/inferiority among people prominently, and being a 'trader' of anything as opposed to being a producer is aspired to. It comes as no surprise that the 'triangle trade' was a relatively Jewish affair and fortunes were amassed by said on the North American continent even prior to the formation of the the U.S.. Funny that BLM and the rest of their ilk seems to forget or never learned these things when identifying 'the' scapegoat to shoulder all of their troubles...if you consider being a natural born citizen of the U.S. rather than of The Congo a 'trouble' which most inhabitants of The Congo probably would not.) Possibly it is related to (((who))) is responsible for their funding (and likely pretty much all aspects of their creation, organization, strategy, and management.)