It’s that Trump supports them.
The racists, neo-Nazis and neo-Confederates support Trump because He Empowers Them.
He calls them very fine people. He listens to them, legitimizes them, gives them the power and the authority to attack Congress. He’s their guy.
In contrast, Desantis and all the rest are mere politicians. They will abandon their support for the radicals the moment it is politically expedient to do so. The radicals know this. They know that Trump is the only one who will support them, rain or shine.
And as a result, Trump is the only one THEY will support.
They don’t care what he’s done. They don’t care about what he might do. They only know that he’s the reason they can walk down Main Street with a flag and a gun, terrorizing those they hate, unopposed. And that’s all they care about.