I think the basis of it probably started with an unequal criminal justice system largely regarding drug use. A black man is/was more likely to get a longer sentence than a white man for the same crime. That began the cycle of broken families. From that point on it was probably the result of perpetuating drug use and violent crime, over-sexualization, and pop culture that glorified it, but at it's core it was depression. One generation of boys who didn't have a dad around turns into 5 and the cycle just continues for many people who either feel stuck or don't know any different. I feel like African American boys are also just naturally more drawn to sports, and when they idolize the most successful black people in that arena, it makes them focus even more on that passion, which draws them away from finding other potential they have that can lead to a more likely successful career. African American girls (and all girls for that matter) who grew up without a dad put a lot of the focus on wanting to have a man in their lives, sometimes to the point of making unwise decisions in an attempt to feel secure, only to be on the wrong end of a bad deal and left to make further bad decisions that perpetuate the cycle. Also, for all of the good that came from the civil Rights movement, there were also some unintended consequences as well. The militant factions that existed in the 60s bred a feeling of animosity that became an "us vs them" mentality that doesn't go away easily. That probably worked to isolate some of those people, which isn't a healthy place to be. I'll never forget something that my grandpa said back in the mid 80s. I grew up in a town with 3 black families, all of whom had kids around my age and I was friends with all of them. The dad's in those families were the president of a bank, a production manager at an aerospace company, and a salesman. They all did well and the families were all involved in stuff. So my grandpa said "minorities do well when they are less than 5 % of the population because they learn to interact with others. When you get above that, they just stick with each other". At the time ( I was like 8 years old) I didn't think much of it. Later on I started to think that was a pretty racist thing to say. Now, I think I see that he's probably right. I can't say that I totally understand it, but my inclination is to think that the more any subset of people interacts socially with others, it creates a feeling of "we". The more they isolate themselves with other like individuals it becomes "us" and "them", and that's not a good place to be.
Poor people have a harder road to the middle class than I did. I was born already there. I didn't do anything special. If I was born poor I'd still be poor. All my mistakes in life were smoothed over by sound advice from family who had experienced success.
When you start a whole race poor you'll have some that make it to the middle class and they'll have to fight racist laws and racism. I didn't have to do shit to get here. Warren Buffett who you mentioned earlier was born rich. He wouldn't be Warren Buffett without a senator father.
The point is that we placed black people in the lowest social class and kept them there. We currently live in a world where black people just flat out get paid less than white people. They are still fighting an uphill battle.