It happens to people. They get into a position where they can take positions and enforce them on others, and spend time justifying it to themselves with calming ideas like "I must know what I'm doing, they put me here, so I'm smarter than they are."
In the process, you find yourself, without humility, ignoring the input of those "less qualified" than you are. The reason it's a problem is that even the smartest guy in the room has something to learn from the dumbest guy in the room.
Example? OK.Al, who headed the mail room at a company near to me, had more vacation days approved by HR than anyone else.
How did he do it? He read the memo, sent out by HR, on vacation days, and sat down with a calendar and played with it for a few afternoons. Partly the result of the mailroom schedule (heavy in the mornings and late afternoons), partly the result of a certain dogged persistence, he had a month off every year in a company that thought it had two-week vacations.
The smarter people above him, who complained about the policy? Two weeks. The smartest people in the room? Two weeks. Learning could have occurred, but apparently, no one was paying attention to him, since he wasn't the smartest guy in the room. He never would be. But he read the memo on vacation days better than the authors in HR.