While, unlike many other people, I do _not_ believe Trump is an idiot, or even dumb at all, I do not believe he has any knowledge of how to stop the internet even if he wanted to.
Plus, how would he send tweets if no internet? I think he likes being able to use Twitter more than he likes being President.
My cursory understanding of the whole "internet going dark" conspiracy is that this would not be used by Trump, but be used by the shadow government in co-operation with "Big Tech" in order to create panic and confusion amongst the masses so they can't organise, feel helpless and ultimately ask for "big government" and "big tech" to step in and save them.
For whatever reason, gp seems to be under the impression that it's Trump who would use this to his own advantage, which is not consistent with the prevailing conspiracy theories.
Plus, how would he send tweets if no internet? I think he likes being able to use Twitter more than he likes being President.