Just because Ferguson was a good manager doesn't mean that he knows how to spot another one. In the same way as being a good player doesn't mean you know how to manage a team. They probably should have been more rigorous in their research and had a stricter criteria. Times are different now and they're living in the past, trying to hire a Scot that can stay there for twenty years. Other clubs are successful even when they change managers every couple of years; they should have accepted that.