Yep, their egos get inflated from interacting with students all the time.

If you have been teaching the same subject for 10 or more years, and you are constantly interacting with people who are learning it for the first time and struggling, it's easy to become arrogant.

I'll go 1 step further and say that most of the advice academics give out in terms of learning has been counterproductive for me.

There have been some exceptions, but I have been disappointed for the most part.