I suggest that wasn't as clear as you think it was to the right people (either through incompetence, ignorance, or bad leadership), or that if they did have some idea that he wasn't a great fit they were hoping that he would produce a miracle that would make all the pain worth it.
Coming in with wunderkind status gives you a lot of leeway with some people, and things need to be pretty bad before the people that hired you will admit that they made a mistake, hired the wrong person, and paid them way too much. Admitting such a mistake does some damage to your ego and reputation of hiring problem solvers. Plus, by many accounts he was producing decent results- after all, he's led some pretty famous projects, and most of the projects weren't regarded as failures, so why should he be regarded as a failure? Other than stealing IP and being a dick, he's not usually called a loser or a failure.
Coming in with wunderkind status gives you a lot of leeway with some people, and things need to be pretty bad before the people that hired you will admit that they made a mistake, hired the wrong person, and paid them way too much. Admitting such a mistake does some damage to your ego and reputation of hiring problem solvers. Plus, by many accounts he was producing decent results- after all, he's led some pretty famous projects, and most of the projects weren't regarded as failures, so why should he be regarded as a failure? Other than stealing IP and being a dick, he's not usually called a loser or a failure.