I have no question that McVay was sorely disappointed most of all . . . . in himself.
I think his bringing in Brandon Staley to coach the D was not just about the D but to get someone to help Coach McVay deal with the defense which was proving to be Kryptonite at times for him. He saw a true weakness in HIS game and he adjusted to make it a potential strength. I think the reordering of the staff was McVay's way to bring in the new ideas having taken what the others already had to offer.
as the saying goes . . . grow or DIE.