Why are people so unbelievably imbecilic?

A personality disorder so that they need to believe someone is in control, otherwise they can't cope with what they see as the ordinance chaos of everything.

Lack of a good education

the American education system does not help to educate people

We’re naturally pattern seeking creatures that can think in abstract. Critical thinking skills are not natural and must be taught.

“There exists in society a very special class of persons that I have always referred to as the Believers. These are folks who have chosen to accept a certain religion, philosophy, theory, idea or notion and cling to that belief regardless of any evidence that might, for anyone else, bring it into doubt. They are the ones who encourage and support the fanatics and the frauds of any given age. No amount of evidence, no matter how strong, will bring them any enlightenment. They are the sheep who beg to be fleeced and butchered, and who will battle fiercely to preserve their right to be victimized… patent offices handle an endless succession of inventors who still produce perpetual-motion machines that don't work, but no number of idle flywheels will convince these zealots of their folly; dozens of these patent applications flow in every year. In ashrams all over the world, hopping devotees of the Maharishi Mahesh Yogi will never abandon their goal of blissful levitation of their bodies by mind power, despite bruises and sprains aplenty suffered as they bounce about on gym mats like demented (though smiling) frogs, trying to get airborne. Absolutely nothing will discourage them.”

― James Randi

Yes, perhaps the most imbecilic belief is the one that all people are equal. Nature doesn't work like that.

We can't all be brilliant like you.

We are getting smarter!

All the bright genes were slaughtered in wars.

Home schooling...

idk, but it's not easy being unbelievably imbecilic...pretty hard to spell too!

That's just liberals.