If such a person chooses the "golden parachute", the "golden rocket" he had to commit on hiring was maybe unachievable in first place...
Even if you're the best for the job, if you don't have the backing of the board you won't get anything drastic done.
Whether those who have the support of the board are really the best ones for the job, that's another question...
From my experience the additional aspect is also that shareholders and/or the management board often have unrealistic expectations on what the company is capable of, and are unhappy when facing reality.
So such a parachute can also be useful to force the company to work through tough decisions, because firing the person who insists on them will not be cheap either.