[n3k5]

I don't know about “McKinsey infiltration into many a large F100+” first-hand, but from context I'd guess it's simply getting consultants from McKinsey & Company[0] jobs in the ‘infiltrated’ firm, on the basis that it has no in-house employees capable of properly setting up / running the bizarrely complex and idiosyncratic SCM-ERP-HCM-BI-etc. software in question.

Basically: You have a problem; Oracle/SAP says they'll solve it for you. Now you have a second problem; they say McKinsey'll solve it for you. Now you have …

[0] https://mckinsey.com