I've met the brilliant jerk (and depending on who you ask, I've been the brilliant jerk). It's a real thing.

One surprising thing is that it is possible for people to change, at least in how they treat people. Once I was told I would have to interact with the "brilliant jerk" and I complained and my manager said, "no, really, he has CHANGED" and, miracle of miracles, he had.

I wish I knew exactly how and why he changed, my best guess is treatment for clinical depression, which often surfaces as extreme irritability.