If he can shrink down the Enterprise and haul it down from orbit with the push of a button
It's funny how we're discussing the believability of the characters' actions and motivations, when this little suspension-of-disbelief moment, the space-elephant in the room, seems to dwarf all other realism qualms in the episode combined — probably by an order of magnitude. Normally it takes some kind of Sylvia/Korob-style magic to pull off something this outlandish, but apparently Flint is a renaissance-man technical genius who's also a Level 750 Archwizard Deluxe.
Hmm, maybe the Trelane-is-a-Q crowd should consider Flint as their next inductee!
Sorry, just being kinda goofy today.