McVay quotes Bill Walsh's book "the score takes care of itself" about building and maintaining a winning organization.

Walsh talks about one of the errors he made was not delegating to the great offensive assistants he had around him (Wyche, Holmgren, Marriuci etc.) as the organization grew.

I think McVay took this lesson to heart with the thought that you build the organization, you surround yourself with great people and then you let them do their jobs and this includes McVay becoming a true head coach and having assistants run the various subsets.