Sometimes when you have a very strong leader, he prefers people around him that are yes men. That works in part because the strong leader has the right intuiti

Sometimes when you have a very strong leader, he prefers people around him that are yes men. That works in part because the strong leader has the right intuition and direction and doesn't need it to be filled by others. But when that leader leaves, the environment was built around him having the big ideas and direction and everyone else is was mostly good at following him. I think this happened at Pixar. So it isn't that Lasseter is irreplaceable, it is that they didn't foster internally the next generation of leaders. And that in turn makes it looks like Lassater was a unique genius.