Somebody surely must have written this already – so apologies to whoever I’m unknowingly following.
Paul Grice was a philosopher of language and meaning https://plato.stanford.edu/entries/grice/#ConImp He’s famous for looking at how conversations work as not just an exchange of meaning but a cooperative interchange of meaning with its own rules and principles.Central to this is what became known as the Cooperative Principle: https://en.m.wikipedia.org/wiki/Cooperative_principle
And following that Grice suggested four maxims which normal conversation attempts to follow. I’ll quote in full from Wikipedia:
Ok, an exercise for the unwary. Pick anyone of those. Now watch Trump.
Did the maxim hold? [Spoiler: it probably didn’t]
Trump is a non-gricean speaker. The maxims don’t hold – at least not in public. Now that is a little unfair – political speakers and press conferences aren’t normal conversations and even the most affable of politicians is trying to manage what they are saying in a way a normal person simply doesn’t have to.
Yet Trump isn’t doing what a politician normally tries to do. He isn’t trying to navigate round these maxims while appearing to be following them. Instead, he is ignoring them and when he hits one it appears more like accident than design. Ironically that makes him seem more truthful instead of less, precisely because he doesn’t sound evasive or hesitant.
In addition, notice how he often violates a surprising submaxim: “Do not make your contribution more informative than is required.” Trump overshares at times – revealing inner thoughts or perhaps comments/argument made by others..
This fluency with incoherence is why I imagine he possibly doesn’t follow Grice-like patterns in his normal speech to the same extent as others. By not following such maxims you spend less effort considering another person’s perspective on what you are saying. That makes it a lot easier to string words together! It’s just that those words don’t make as much sense as part of a conversation.