So they go after and arrest Trump on a politically based charge(it obviously is).
He is convicted and can't run and De-Santis takes his place. 
Take the politics out of this and think of this purely as a strategy.

My current view
Trump would win the nomination but would struggle in the  General Election.
Desantis would not win the nomination but would do better in the General Election.
I would rather have Desantis (less baggage)

My Prediction if Trump is convicted of a felony
If convicted he can't run for the Presidency, DeSantis gets the nomination and wins the General Election.

My Prediction if Trump is not convicted of a felony
Trump gets even more support and overwhelmingly wins the nomination but loses by a small margin in the General Election.

If Desantis wins he would still have to deal with the press and the Rinos. Part of Trump's problem
is he has daggers coming from both sides which is beyond me how badly he managed it.  I do 
know if he is possibly elected he would be smarter this go-round.