He wasn't that intelligent. He tried to appear intelligent and most people swallowed it.
Most of his supposed knowledge was poorly understood new age Philosophy.
Arnold is/was far more intelligent.
He was a junkie nutjob and was so intelligent he poisoned himself into a premature death and walked around in his pyjamas.
i think mentzer was pretty intelligent, but i also think there's many kinds of intelligence. for example, musical intelligence, logical intelligence, social intelligence, etc. therefore i'd say mike had a high degree of logical intelligence, but arnold... no he's a freak of social intelligence, in the genius range!!!! by the way, pretty much all of the greatest con artists have had a Superior degree of social intelligence
but, i'm not saying arnold is a con man...