The real deal smart people are almost always humble...

[Mister Obvious]

I say “almost” because I know there are exceptions...

But I’ve personally never met one.

They are basically always so humble about their intelligence that they’ll barely admit to it.

I wish to mate.

[Mister Obvious]

[Sober Fungi]

I have also found sometimes its dumb people hiding their dumb or psychopaths hiding their true intentions by acting humble.
I guess it depends on the personality type. I have known smart people who were jerks some who were nice.

[Malal]

It's because, if someone gets the impression that you're smart, they'll stop trying to understand you and just assume you know everything. I don't know if I'm smart, but I know I hate other people thinking I am. Comes with all sorts of stupid expectations, so it's not logical to project that image. And even in the rare situation that you want to appear intelligent, you can't be direct about it - makes one come across as a spergy dickhead. So.. yea