Gish gallop is a rhetorical tactic that only works with high school debate teams and right-wingers. If his post was just a short denial of being associated with Epstein or a short statement telling people to stop talking about Epstein, it would be very easy to people to refute just by posting pictures he took with Epstein. The narrative would be very simple: "Don't investigate my paedophilia."

When it's phrased this way, he's calling in so many conspiracy theories and irrelevant issues that you can't choose one thing to respond to unless you're literate enough to understand subtext. His defenders now have X number of reasons to rally behind him during a moment that looks really bad for his administration. Those things are each loyalty tests which confirm the legitimacy of everything else mentioned. If you pick one to respond to his supporters will just throw all of the others at you like insisting you don't see the bigger picture of everything being true+false. His audience can't separate those things into separate issues while his critics don't have the time to respond to all of it and parse the nonsense.