I've worked with some "brilliant jerks" before. But they were never the type to cover on holidays, bring in the most revenue, etc. The brilliant jerks I knew tended to be selfish and negative. Perhaps he didn't share the company vision, but this guy didn't sound like a jerk (well, until he started suing the company after he left).

I will say that the true jerks have a way of worming their way into the company. For example they'll do a lot of work with the goal of making sure they're the only one who understands some certain process. Then they horde knowledge and never want anyone else in there or any documentation to exist. The team is afraid to fire them because nobody knows or has the time to learn that part of the system.