He has done a lot.
Democrats help Blacks like the slave owners did. They provide benefits (food, housing) and they would rather blacks keep accepting those benefits than become successful in the marketplace. Granted, they try to bribe now, rather than use force...an improvement to be sure. But the Dems still try to keep Blacks needy for those benefits (social programs now) so the Dems can keep harvesting...used to be cotton that Democrats harvested from blacks but now it is votes.
Trump was opening the market to the lowest unemployment levels for blacks, which is a real problem for the Democrats retaining power. If urban blacks become successful in the marketplace as a group, they will feel less compelled to vote Democrat. The Dems have to prevent that at all costs.