It is common in RPGs to have you attempt convince others using your charisma or similar stat. In real life tho, I usually try to do so using Intelligence sort of. I assume my fellow human beings are able to be rational and I refuse to entertain the idea of them being dumb to the point where there are things they can't understand if I explain it to them. I also assume I'm not dumb to the point there is stuff I'll never understand even if they explain it to me. (Of course, there multiple approaches to explaining stuff, so it won't work sometimes not because of the idea being incomprehensible, but because the approach wasn't the right one.)

So, if a human can understand something, there is no reason another human can't understand it as well. Based on that, when I try to convince someone, I'll usually rely on formulating arguments and/or pointing logical flaws in theirs. So, in a rpg context, I kinda see it as using intelligence instead of charisma.

Assuming that game designers are thoughtful professionals, I suppose there is a good reason they usually put persuasion mechanics as strictly charisma-based things without any sort of intelligence-based conversational skills. Of course, there are ideas of balancing, but looking for example at dnd 5e, in most cases, charisma is just better than intelligence. Also, RPGs generally are just too big and to varying to really be fully balanced. Coherence with reality (simulatory elements) is often behind many design choices.

So, here's my question: how much would it be reasonable to use intelligence instead of charisma to convince people in general? Am I jus too Fe blind to realize how essential charisma is when interacting with other human beings?

Also, if we want to dive deeper, if we aren't convincing people using rationality, where is the line drawn between charisma and manipulation?