Massive L for DeSantis. Even if Biden isn't popular, with Trump likely taking upwards of 10% it wouldn't be much of a contest.
While Trump getting upwards of 10% is extremely unlikely, in the event that he does, Biden is basically a lock for re-election, full stop.
If Trump could hypothetically get the resources to run as an independent (unlikely, he isn't that rich), he would get over 10% easily: he has a rabid group of supporters who like him more than the Republican brand. Wasn't there even talk about Trump starting a new political party? He would eat into DeSantis's share, giving Biden a layup win