A Chinese national once told me that individually people are quite intelligent, but as a mob they go insane.
And then there’s the Suffragette song from Mary Poppins
“...Although we adore men individually, we must admit that as a group they’re rather stupid.”
People can be highly intelligent—but if they are brainwashed by “experts” there are very few willing or able to do the hard work to break the spell.
That requires determination as much as intelligence.