Apparently needs to be said again. Why were most Black Americans Republicans until 1968?
Both parties were extremely, blatantly racist until about 1968. Yes, that includes Kennedy and absolutely LBJ. But while the Democrats tried to soften that with Civil Rights rulings from the Republican Warren's Court and then legislation, the GOP led by Nixon decided they didn't need people of color after all and went more openly racist. Then illiberal under Reagan and the Bushes and then fascist under 45.