There are always exceptions but pretty much class mobility is limited in america. Very few people born middle class will become billionaires and very few billionaires will become middle class.
Its rare enough that you can almost ignore mobility all together except mobility within your class. Where maybe your parents made 100k and you make 350k but your kids might make 150k. Minor shifts that seem big but dont really equate to a class change.
The point is that its rare for people born into middle class to fall into poverty and its just as rare for people born into poverty to make it to middle class.
So when you force several generations of African Americans into poverty with racism, redlining, unequal pay, the lack of benefits for vets returning from WWII, worse education, segregation, etc etc, what you end up with isnt a race that's poor because they are naturally worse, but they are poor because we supress class mobility and we put them into poverty.
It will take generations to repair but the littlest things we can do now would help. As someone who hires, I am often left scratching my head at some resumes I get, I dont hire those people because their resumes are bad but who taught you how to write a resume? Typically thats a generationally passed down skill. We can jump start growth by investing in programs designed to teach some of these things that are learned through observation of generational success.
But its easier to just tell poor people to work hard so we'll probably just go with that even though its not the solution.