Correctly or not, Trump clearly feels betrayed by DeSantis' run in a way he doesn't for the candidates that he was less influential in their careers.
Add to that that DeSantis is the clear second place, and yeah, he's going to get the full Trump. I seem to remember Trump coming hard at the other R's in the 2016 primary as well. He had little nicknames for the top three or four.
If Trump doesn't give you a mean nickname, it means he doesn't think you are really an opponent.