Using Vermiel for an example I think the addition of Martz was a crucial part of things falling into place for a couple reasons...
First off, Martz looked at the film of Banks and told Vermiel they'd all be fired if they didn't upgrade. The moves that happened to acquire better players, who turned out to be key players, grew out of that OC hire.
Second, Martz is a great teacher of offensive concepts. Everyone was dazzled by his scheme, but it was not the scheme that set him apart from most other coordinators. It was his ability to teach that offense an immense playbook install in one camp and have everyone know it cold. That was not the players. That was the coaching. With the OCs the Rams have had that same collection of talent probably would have struggled to be on the same page and the bitching and moaning would start along with turnovers and Vermiel would have been fired most likely.
The point of course is that coaches matter. It is not just about the players. In fact it is very rare to see a player who is so good that he'll excel no matter who coaches him. Gurley is an obvious example, where he could play in a run or pass heavy concept offense with smooth transition. But the rest of the guys on offense need to be well versed so they'll be able to play fast and not be slowed by needing to think and being confused on responsibilities. It's early but Boras seems to understand that. And if he does get this same bunch of guys to know his offense cold they're gonna play fast and people are gonna be shocked by how much better they are.
You made my point for me. Coaches who are "successful" in the NFL always seem to have a stellar QB to rely on. Not very often, especially in the modern game, do you see coaches succeed without what could be considered a HOF skillset from the QB position. Minus Joe Flacco in 2013 (I really don't think he is all that great) you have to go back to 2003 with the Bucs to find a SB winner who didn't have a future HOF (lots of speculation in Seattles part on Wilson I know) at QB....and the Ravens prior to that both of which fielded defenses for the ages. Going back even further you have to get into the first couple years of the 90s to find Mark Rypien and Jeff Hostetler as non HOF worthy QBs.
Ron Rivera was on the verge of being canned himself until Newton managed to turn the corner. Mike Tomlin has had sustained success behind a terrible human being but a good QB in pit. Pete Carroll was all hot air until Russell Wilson put that team on his shoulders. The big cheat in NE, who knows what would have become of him sans Brady? Would Mike McCarthy have a job in GB without Rodgers?
Players cost coaches their jobs, not the other way around. And its easy to tell when a coach is in way over his head (ala Linehan for example) versus players not being able to execute a game plan....which we see far too frequently with Fisher (find him a QB, and it better be Goff, and this thing should be an afterthought). Scheme stability is worth more than rotating coaches as far as I'm concerned.
Rare or otherwise, the players that perform regardless of who the coach is are needed to get to let alone win the SB. It is a team sport, but without excellence leading the team there will be no team success. Rotating coaches without a strong roster is just spinning the tires. And we have seen over the past few years Snead and Fisher know how to find players and develop them. Light years ahead of anything else we've seen in this century as far as the Rams go for that matter.