That you're only as good as the players you have on the field.
Coaching has a huge impact on the game. Great ones get all 11 on the same page quickly, get them all playing fast. They don't put up with guys who loaf and the non-performers. They build a confidence among their players week to week through the season. They properly align their needs with the front office and scouting dept. And most importantly they WIN more than the lesser coaches.
But in the end the players have to make the plays. Cooks didn't haul that catch in during the SB, if he did who knows what happens. Goff didn't see his WR wide open in the SB and the late throw was incomplete, if he was on-time with that throw it's almost surely a TD. In fact in just two years of Goff's regression since that game McVay went from a golden boy offensive genius to a guy people are openly questioning on every Rams board.
What sets him apart, though, is that he cut bait on a QB they had just paid who wasn't living up to expectations. 99% of head coaches would not have the cajones or the ownership and front office support to make that move. And it's going to pay off.