The problem I see with some pretty smart guys is that they develop a tunnel vision. That means they are so focused on one or a few areas of expertise they forget the big picture.

Not only that, biggest problem is that as “smarter” guy gets ( or more valued in their field) they are less willing to question themselves, or accept new opinions.
So at the end we get funny situation that lot of “experts” are kinda close-minded stubborn folks.