Most Republican candidates, since American blacks entered the Dem plantation early in the 20th century, know they can’t successfully woo black voters with a conservative message of self-reliance, law and order, and the work ethic. So they didn’t try. They know it’s not what the vast majority of black voters are looking for. With the exception of about 5%, they are looking for government handouts, having been conditioned to expecting them for generations (not that they ever get enough from the Dems to satisfy them). Rebublicans (like Trump) will never out-promise the Dems, and their conservative message won’t resonate; ergo, they will continue to be relegated to low single digits in the black vote. If Trump is elected he might get more than 5% of the black vote in a re-election bid, but nothing approaching 95%.
An embarrassingly preposterous prediction Trump had no need to make and which makes him sound like a blustering buffoon.