At least in part, it’s the 20th century political alliance between black politicians and white social liberals. These are not problems that existed in the first half of the 20th century. Ironically, you’re now seeing the same social breakdown in working class white communities, who historically were aligned with white social liberals. Fatherless “barstool conservatives” are the product of that alliance.

Almost all the disparity in income mobility between black and white people is caused by disparities between black and white men. (Black women have similar mobility to similarly situated white women in terms of individual income.) And Harvard’s Raj Chetty has shown that the two things that eliminate racial disparities in income mobility for black boys is growing up in a neighborhood with (1) low levels of racism among whites; and (2) high levels of fathers living at home with their biological children: https://academic.oup.com/qje/article/135/2/711/5687353. There’s only a handful of places in America, unfortunately, that meet both criteria.