I don't think DeSantis will run against Trump because he respects Trump and wouldn't want to undermine Trump's 2024 run with a contested primary. It could be argued that Ronald Reagan's primary challenge undermined Ford's re-election run against Carter.
Nixon was so hated around that time, that it would have been
nearly impossible for Ford to be re-elected. He was viewed
as a man that had been appointed by the evil Nixon, and that
would have been a pox on any political candidate.
It would seem to me that a primary win for another candidate
that year may or may not have helped the Republican’s
chances. I think it was a pretty done deal going in.