Charisma isn't about looks anyway, it's about charm and force of personality.
Yup ... and itelligence is about how well can your character grasp new concepts, remember stuff, and learn things.
Notice what isnt there?
Constructing(?) sentences.
Well...rag...to be able to speak, write and read...you kinda need to learn how to do it, remember the words and grasp the concepts of grammatics etc :P
That said, for speach, not a very high intelligence is needed.
And, I get your point. There are illiterates that are still highly intellectual.
