Wherever there is a strong black presence in the state, there is black representation (I.e, Moss Point and Jackson). I’d be willing to bet that every town and city that is predominantly black in the state, is represented by a black politician or a Democrat.
Again, Mississippi, while a heavy black state, is only ~38% black while whites make up ~58%. While more could be done, Black Mississippians are doing an admirable job when it comes to placing those that look like them in positions of power. Their local politicians(governor, senate, representatives, mayors, etc) have failed them.