Trump sometimes doesn't understand that his brand of attack only works against people who are mostly "unlikable", like Hillary, Cruz, and most of those he ran against in 2016. Musk might not be the most charismatic guy, but he is an iconic figure who has a very large fan base, not to mention being the richest man in the world. The people who hate him are never going to vote for Trump anyway.
Imagine Musk tweeting "DeSantis 2024". That'll get a lot of people to vote for DeSantis.
If I were DeSantis, I'll be spending time with Musk. DeSantis should go for it. Trump was great. But nobody owes him the nonimation in 2024.