I was 6 or 7 years old. The walk home from school was, as I recall, a rather long one, probably close to a mile. It was winter, cold and snowy. The two boys were big, probably in 6th grade. They were not kind. They took off my hat and stuffed it full of snow. They stuffed snow down my coat and shirt. They took off my gloves and stuffed snow in them. Then they laughed and walked away and left me to continue my long walk home in the cold.
So at a very early age I learned that at least some people are capable of being quite cruel and inflicting pain on others with no apparent remorse. I have no trouble believing that the world is full of such people and that many of them have succeeded in "making it to the top." And that there are others, equally cruel and callous, who are willing to do their will, for the proper price.
So when I hear people dismiss conspiracy theorists for all sorts of psychological reasons -- one commenter even said it was due to our "fear and tribalism" -- it falls off me like water off a duck's back.
The psychology of this conspiracy theorist is quite easy to understand: reality.