Rescueing a fail[ed|ing] project takes a very different skillset than managing one properly in the first place. Planning and executing is a hell of a lot easier than firefighting through a storm of finger-pointing and blame-shifting. Once things have gone wrong, most people involved lockdown and stop being helpful for fear of being seen as the one who made it go wrong. Managing that is a rare skill.

Ideally no one would risk projects going awry by employing "average" project managers and then having a single "rockstar" guy to sort out the mess if they do go wrong. It'd be far preferable to have brilliant project managers for every project. But pragmatically, that's never going to happen, so we need the "rockstar".