Trump is not fucked. He'll be allowed on the ballot even if he's in prison, and the only reason he's going along with any of this is because he's afraid Biden will imprison him if he doesn't, and because every mug shot gains him points in the polls and keeps him relevant and talked about.

And once he wins he's just going to walk out of a jail cell unlocked by a loyalist and then execute anyone who tries to get him back behind bars as a traitor.