Like, why New Mexico could get away with not having a metal detector in its state capitol building, but California would be ill advised to do the same. As a group, we wouldn't handle a lifetime of that kind of limitation on our freedom of movement, very well. Nor would our relatives.
If what you want is a government run by the best and brightest, then in setting up your country, you should see that small is beautiful. Don't set up a vast empire. Create lots of little countries that stand together for mutual defense - an alliance, not a vast union.
Don't leave any one man with so much potentially abuseable power, that to wield it is to spend the rest of one's life looking over one's shoulder, and needing to worry about what somebody will try to do to one's children.
That won't just draw narcissists. It will tend to weed out everybody else. That's the problem, right now. Trump SHOULD be meeting with real opposition, right now, but he doesn't, because he is surrounded by people who aren't nearly enough of an improvement over him.