My first senior engineer was a "brilliant" jerk. He had decades of experience, but when I started digging into his work I realized that he was useful mainly because he was offering solutions to problems that he created. I've heard some people say that a good engineer will eliminate the need for his/her own job. This guy was actively creating a need for himself by causing problems without management realizing it.

About 1 out of every 10 ideas was a good idea, but you had to know how to filter out the bad ones. If you said "no" to one of his bad ideas, he'd say that you weren't listening to his input and complain to your manager.

He was abrasive, condescending, and dominated every meeting. If you said anything to management, their response was "Oh that's just Bob, what a crazy, quirky, eccentric guy!" What they refused to realize was that being Bob's peer was very different than working for Bob. What management perceived as a quirk, was a character flaw that made life hell for anyone working underneath Bob.

And to echo other comments, nothing was done about Bob because management didn't want to take responsibility for the culture of the company. Why risk negatively impacting profits by actually managing your employee when you could blame it on millennials being whiny and you believe that engineers are interchangeable?