In the ancestral environment there were no abstract disciplines with vast bodies of carefully gathered evidence generalized into elegant theories transmitted by written books whose conclusions are a hundred inferential steps removed from universally shared background premises.
In the ancestral environment, anyone who says something with no obvious support, is a liar or an idiot. You’re not likely to think, “Hey, maybe this guy has well-supported background knowledge that no one in my band has even heard of,” because it was a reliable invariant of the ancestral environment that this didn’t happen.
Conversely, if you say something blatantly obvious and the other person doesn’t see it, they’re the idiot, or they’re being deliberately obstinate to annoy you.
And to top it off, if someone says something with no obvious support and expects you to believe it – acting all indignant when you don’t – then they must be crazy….
I have a tactic which has greatly increased my scientific eloquence professionally. Expect I’m speaking to someone with the intelligence of a rather dim child (about 10yo) and jazz up the vocabulary as they become accustomed to the concepts. Be heavy-handed with metaphor and make fun little anecdotes or examples, which tend to stick in lt memory.
A clear argument has to lay out an inferential pathway, starting from what the audience already knows or accepts. If you don’t recurse far enough, you’re just talking to yourself.
If you dumb yourself down to begin with, human nature means the other person will show off (every single time) and you can see their intelligence level in what they think is The Best (in fact their personal best), and also what they value to leverage in persuasion e.g. pieces of paper/academia/authority figures, empirical truth/data, moral outcomes/personal feelings.