He does poorly among AA, that's why he is Vulnerable to a Charlie Crist challenge, he would lose the Midwest to Biden with only IL as the only Latino state.
That's why he did poorly with Gillian. If he survives a Charlie Crist challenge in 2022, which he wont
To be fair to DeSantis, he was behind well-outside the margin of error in all public polling in 2018 against Gillum (I don’t recall a single one where he was ahead) in a Democratic wave year, and won. So it was actually more of an upset that he did win.
If you look at a source from “the center square” from Nov 27, 2018 (again can’t post the link until I get to 20 posts), he got an unexpected boost from black women regarding his stance on school choice, so that could have made the difference.