I'm not sure the label "dumb" fits. I recall seeing an interview with one of the Watson and Crick guys, forget which one, but he was, clearly, demeaning and patronizing towards people of faith, being an avowed atheist, sure he was mentally superior, wearing that "legend in his own mind" syndrome on his sleeve. It was painful to watch him make such a horse's rear of himself. His behavior was affected, laughing at his own jokes incessantly, as if so amused by himself, talking to the interviewer as if he wasn't even there, going on and on like some self absorbed idiot. In short, the dude came off this way, painfully so, clear he couldn't see how ridiculous, childish and self willed he was being, or he would have known better: thinking he was being brilliant, he was, rather, making a fool of himself, was beneath dignity for his blinding ego. On the other hand, this man was a Nobel Prize scientist, could not be generally dumb.
I think such aberrant behavior is more a matter of spiritual blindness, the inability for some people to see some things for, very often, blinding ego, the carnal human tendency to self will and to believe what we want to believe, at the expense of even clear truths, to the contrary. Spiritual blindness often looks a lot like utter stupidity, and I suppose is, in a very real sense, yet it is the domain of many of the world's best minds.
Have you ever asked yourself how intelligent people of “faith” could subscribe to cults, which contradict clear scripture, God’s holy word? We have multitudes of people who claim to believe in Jesus Christ, while disbelieving some of the Lord’s basic teachings and commandments. Have you ever wondered what on earth is wrong with people, claiming the faith, whose religion scripture states is wrong? Who cling to their cults, all the lies, despite the very word of God? Can anybody be that dumb and functional, at the same time?
It's a very curious thing, the likes that people who, for instance, no matter how religious reject God, refused Jesus Christ when He was physically present, though He worked amazing miracles to prove His credentials, scripture itself with hundreds of detailed, fulfilled prophecies only God could predict. The proof is all there in our Bibles, yet you could find Nobel Prize type scientists, by the bushel, who, presented with the utter statistical impossibility the prophecies of the Bible could be random (Isaiah 46:9-10) will, nonetheless, reject the very notion of God. Scripture points this very thing out, Luke 16:31. In short, there are, otherwise, brilliant people who are putty in the devil’s hand, real dupes, spiritually blinded, who will sign-up for the most absurd lies, even mathematically impossible lies, but lies that tickle their ears and egos. The Lord can part the Red Sea, but some people will go off and worship a cow statue, somehow make sense of it, many with surely triple digit IQs. Presumably the Pharisees knew the scripture of the Lord best, yet what good did it do those spiritually dead? All that knowledge, that murders the prophets? Men of letters that didn’t learn anything from simply Cain and Abel?
So, sometimes it's blindness, which mysteriously trumps intellect (pun unintended!) and appears as dumbness, to the sighted individual. Spiritual disease is more intellectually debilitating than most mental disease, can make otherwise smart people fail to see the obvious, hence making idiots of themselves. This also well points out how the foolishness of God, if there were such a thing, is wiser than the wisdom of men, Isaiah 55:8-9.
Do yourself a favor, and don’t hold your breath there are any saviors on the ballot. The only thing that can be said, for certainty, is only a Godless fool would vote for Hillary, though I’m very uncertain what a vote for Trump and a dime will actually get you, anymore.