I think it is fair to say that Johnson is intensely loyal to his coaches and to his former players, many of whom he hires as coaches. I spent the summer reading Rick Atkinson's three-volume opus on the U.S. Army from the lae '30s through victory in Europe, and Tom Ricks's "Generals", about, well, U.S. generals. I do not recall which author observed that the difference in the military in WWII and today is that in WWII, generals got fired and performances improved. it did not always derail their career, but it replaced them with somebody more capable in that moment. But incompetence was not accepted.
It is not an overstatement to say Johnson doesn't fire anybody. Throw out a couple of DCs in 10 years and you have about done his firings. It is complicated by his hirings. Maybe the uniqueness of the offense requires him to hire former Navy players, to keep them on staff, and to promote them. I don't know. I don't even know it directly affects coaching skills or development. But the fact is they don't get fired no matter what happens on the field. It is admirable that Johnson takes all the heat, but those missed blocks, missed assignments, false starts, botched handoffs, bad tackling angles, missed tackles, horrible reads, all of it, is the responsibility of assistant coaches somewhere in the chain.
Whether that is an answer I don't know. But in the best melodramatic sense, mistakes were made. Who fixes them?