In mgmt consulting at least, being bright is actually important because it is immensely important to be able to put on a guise of competence and mastery to your client even when you have no idea wtf is going on. "Looking and sounding the part" is one of the selection factors.

My friend once told me that the most important skill he picked up at one of the big 3 firms is to appear utterly confident in his ideas and proposals when in reality, he had no idea what he was talking about. (then again, these guys will then turn it around and actually learn a crap ton about the industry in the following 2 days by pouring over research)