They both have too big of egos for that. Trump doesn’t like DeSantis because A he thinks he’s a lame nerd and B he tries to steal Trump’s spotlight, and DeSantis would never accept the second pick.

DeSantis is considered a viable back-up plan in the event Trump kicks the bucket or is prevented from running for office for some other reason. Desantis has a lot of money behind him (i.e. institutional power). Trump will never be comfortable having a suitable replacement sitting second in line to the presidency and people with deep pockets who stand to benefit from his demise. Mike Pence was a good choice. He was an uncharasmatic freak and Trump's supporters would sooner kill him than see him take over.

It might still happen, because the people with the money make the real decisions, but it would be an extremely uneasy relationship.