Not because the person was wrong for the role.
Because nobody wrote down what the role actually was.
I have seen it happen more than once. A senior leader joins a company fractionally, the relationship starts well, and then month by month the scope expands more standups, more strategy sessions, more Friday emergencies until they are doing the full job on a fraction of the pay. Not through bad faith. Through the natural pull of a company toward someone whose judgment they have learned to trust.
The contract is the only place to stop that before it starts.