>Einstein was, by all accounts I've seen, a pretty nice fellow.

Except to his wife.

Einstein's breakthroughs happened alone, in a tiny window of highly productive years in his twenties. The rest of his life contained little of note and he never needed to build a huge/excellent team to accomplish what he's famous for. The "asshole" aspects of famous business leaders occur because they need to drive enormous groups of people beyond what they thought they were capable of.