IMO, we discount the role that slavery and Jim Crow plays in this thinking. Blacks were rescued from slavery by a strong fed govt. Blacks were freed from Jim Crow by a strong fed govt. The dominant liberal ideology of Black culture is a continuation of that support for where their freedom came from. It is such a strong part of the Black culture that it is a part of their religious beliefs.
Then they should be supporting Republicans. Lincoln was a republican and it was Lincoln who brought about the emancipation. And it was democrats who did the Jim Crow stuff. And it was democrats who donned the white sheets (Robert Byrd). And it was democrats who reintroduced slavery via the great society. And it’s democrats who are killing black babies at a horrendous rate. And it’s democrats who want all of black America on the reservation.