The most common cause of stupidity is brainwashing. The masses are defined by their susceptibility to approval seeking, and it's this vulnerability that leads to mass psychosis.

It's generally dangerous to try and tell them so, and after all the trouble has arrived and the outcome is clear, they will then pretend they didn't believe in it even though we all know they persecuted us for saying there was a problem.

Never walk blindly into a seething crowd. You don't know when the panic is gonna hit. And trying to save them is likely to get you killed. There's a popular story about this happening to someone.