He gets away with being the new manager, strings a few winning streaks together and everyone seems happy. The following season he gets a winning streak then goes on massive losing streaks. Fans are then alerted to the team having no plan B and a lot of the time just seem to struggle through games. He'll then nabble a few wins to keep a team up.
The following season he'll start badly even after a full pre season and new signings, the football is exactly the same. fans realise he is a fraud.