I think I know why the intelligent among us are not running the world. It's because humans are distance predators.
Stick with me.
It's an evolutionary survival tactic. We're soft, hairless, not very strong, very well armored, or pointy in any way like your typical predator. What we are is persistent.
We can't outrun a cheetah. We can't wrestle a mammoth to the ground. But we can wound them, and follow them until they literally drop dead. We go the distance. And that's where stupidity comes in.
The intelligent and the capable are exhausted by the energy it takes to exist in a world below their capabilities. It takes effort to step their internal engines down from what is a natural speed to something that's digestible to the middle/left of the bell curve. (For the record, I'm including myself in this as a representation of both sorts as in some ways I excel, and others I am a blight on the landscape.)
Spend too many processor cycles on holding yourself back, and you go home at the end of the day wishing only for a bit of your favorite vice and for the kids to stay off your lawn. And while the mighty have a bit of a lie down, this gives room at carcass of power for the lesser able to run about, grabbing chunks of the fatty liver or precious marrow.
Average pays dividends. Always has, always will. And I still want nothing to do with it.