I'm sure they have smart people, but they're not that exceptional imo. Otherwise mid-way through they'd have surely realized the impossibility of the situation, notified the city that the original objectives are unattainable and all presentations, documentation and suggestions clearly stated that their new goal is not to "stem jail violence" but lessen the "contrapositive" (out-of-control violence). I bet none of that happened, not because McK doesn't have smart people, but because they're often not really trying to "solve problems".

Often, I don't think you hire McKinsey to solve your problems - you hire them when your problems are already out of control and you need to deflect the blame. They give it their best shot, if they turn it around then they're heroes, if not, you can blame them and they still get paid.