I think that a key factor is that ever since the Mexico trip, Trump is proving to the other side and middle that he’s not bats**t crazy. This means that some bernie supporters and other disgruntled dems will vote for him. And those that simply can’t pull the R lever will either not vote at all or vote third party.
i.e. He gave the hillary haters on the left and middle permission and comfort in either voting for him or not voting. That latter group is what will cost hillary. I can imagine a LOT of people in the black neighborhoods simply not voting.
This also bodes well for the Republicans running for other offices in those areas.
In the last two elections many black voters came out simply to support the first black president. Hillary wins the black vote but she can't possibly energize the vote the way Obama did. She's just too old, boring, and... not black.