Clever stupid, do you know this person?

I’ve noticed one thing; stupidity is not the opposite of intelligence. I’ve seen now many times people I know for a fact to be very intelligent and capable, just continuously fail to be prudent, failing because of it. I’m thinking probably the people who caused the financial crisis were pretty smart, and that they were probably pretty stupid too.
So what do you think? Have you seen this kind of duality too? How do you safeguard against it if the person in case is your boss for instance, or a vital part of your organization?