He doesn't have to do well with black voters. He just has to suppress their votes enough.
(Remember the stunt they played with ex-felons... a group where black males are disproportionally represented. In a referendum florida voters said they should have voting rights restored. So the republicans in the state changed the rules to have released felons re-classified based on whether they had paid some fees.... and then wouldn't tell a bunch of them how much they owed.)
My hope... Deathsantis will have is little fiefdom in Florida (because Florida be cray-cray). Republicans will think he's the next greatest thing in politics because of his success in Florida, but when he tries to run for president he gets rejected in a general election because the rest of the country recognizes him for the hard-right blowhard that he is.
DeSantis has national appeal. Much more so than any Democrat.