business types and intelligence

Having met and known a number of businessmen throughout my life, I am usually bothered by one observation general in its attribution. Without fail, they seem to lack intelligence. I do not believe this is the case with all businessmen, and that some may be of very high intelligence, but of most. Am I misjudging things, misunderstanding bad manners and offensive attitudes as some kind of uncontrollable idiocy? Surely, to run a large company requires above average abilities? Except that viewpoint does not necessarily reflect reality as so many business people I know have acquired their money in a multitude of unethical ways that only the very stupid could engage in. Success in business seems not to require intelligence but other aptitudes.