It is easy to be stupid
Sometimes I see people do or say stupid things, and I wonder how those people can be so stupid.
But when I think about it, I realize that it is really very easy to be stupid. There are many different ways someone can be stupid. Some people are poorly educated. Some people may be born retarded or with some genetic defect. Some people may have brain damage from lead poisoning. Maybe some used illegal drugs that caused brain damage. I could think of other ways, but I am sure you get the point.
It is only when everything in the brain functions correctly that people are not stupid.