DeSantis was considered one of the heir apparents of the MAGA movement. But the longer he stays at this, the faster and further he falls away.
Trump didn't say "he's a RINO globalist
if he runs a against me", nor did his supporters. Trump's accusations - and your repetition of them - wasn't conditional on DeSantis running. It was stated as already proven fact. You've flatly stated you wouldn't want him as VP in 2924, and wouldn't vote for him in 2028.
So there isn't any "the longer he stays at this" element to this. You, Trump, and the rest of the MAGA crowd already have marked DeSantis as no better than Jeb, Romney and the rest.
If DeSantis backs out now, he won't have the national stage to refute what Trump has said about him. He needs to run so he can defend himself and attack Trump hard from the conservative side. Go after Trump's empowering of Fauci, his nomination of Gen. Milley, who is the worst Chairman of the Joint Chiefs of Staff in history, his exploding of the federal deficit, etc. etc.. and hopefully bait Trump into to saying something incredibly stupid and offensive to voters.
Backing out now would be backing down from a bully, and that's not good for someone who wants to be President someday. Better to sweep Trump's leg, and do whatever is necessary to beat him.