Why? So Trump can win Florida? Or get 99% of the conservative vote instead of 98%? Trump will nominate a woman. Kari Lake has the MAGA energy. Probably her.
DeSantis is a national figure. It *might* even get the RINOs not to stab him in the back quite as much and would probably please some of the large donors.
For DeSantis he gets some influence within the administration and a clear path to the Republican nomination in 2028. Otherwise he might have to fight off Kari Lake and/or some other strong candidates and its no guarantee he would win.