Most of the time though, the jerks just aren't even close to being brilliant. I feel this jerk attitude is quite often something that is used to mask ineptitude.
This is after 20 years, 7+ companies and quite close work with hundreds of individuals (often in a managing position, so maybe they think I was the jerk ;P).
(In fact I feel like most of the "brilliant" people I have worked with have actually been nicer than the average person.)