You're calling out a correlation, not a cause and effect.

Companies that are growing quickly, money coming, happy investors, don't hire McKinsey to make drastic changes to the company. They don't need to.

Companies who aren't growing, money is a problem, and investors are asking "what the fuck"? Hire consultants to make major changes.

It's similar to companies that go into bankruptcy. They often hire CEOs that are skilled in winding down operations, selling off parts, taking the company through bankruptcy. Someone needs to do that, it's not simple or easy to do well, so they are very well compensated. Then people complain why this CEO go a bonus when the company is filing for bankruptcy.