If Trump were to take DeSantis up on his offer of protection, it makes Trump look weak. Trump would be a fugitive and thus become a prisoner in the safe haven of Florida. Other governors are not as likely to be as solicitous to the ex-president so presidential campaigning would be greatly curtailed. Plus federal marshals might be employed to frog march Trump out of Mar-a-Lago.
Not to mention, if Trump refuses to surrender and goes on the lam, that only makes him look more guilty---and cowardly.
As a bonus, DeSantis, a Harvard Law School graduate, is also vowing to violate the U.S Constitution. Article IV, Section 2 reads: “A Person charged in any State with Treason, Felony, or other Crime, who shall flee from Justice, and be found in another State, shall on Demand of the executive Authority of the State from which he fled, be delivered up, to be removed to the State having Jurisdiction of the Crime.”