The man must have wielded enormous personal influence over Board Members for them to have not applied standard performance evaluation/consequences procedures to him for this long.
The details of how he accomplished such influence over them, what was used, how he did it, that would be a historical story of value. The people who could have removed him earlier didn't just wave their fist and say 'Gosh, Steve will do better next time, we know he will, you'll see...'
So who were the people that kept him in for this long in full view of numerous consecutive failures, what did they get out of it? That would make a good investigative story.