The decision to use Ryan is completely defensible. Neither team had a good rush attack that night. It was a battle of the quarterbacks for the whole game with both sides only really using their pass catching RBs for most part. We used White, they used Devonta Freeman
The problem with using the running game effectively in the Superbowl is that both teams had excellent front 7s. leGarritte Blount for all his faults is a decent power runner and he got humiliated. We put their big RB on his butt a couple times too. The possession game just wasn't there for either team and both teams had easy penetration of the middle of the football field through the air, and a miserable time doing the same on the ground.'
So the question is, why would you use a unit that wasn't getting the job done all game, to close out a game? It'd be like rolling in with the long man in the bottom of the 9th with a 1 run lead, sure you might get away with it but is that the best way to use your resources? Probably not.
It's a simple philosophy that I've seen Bill use a dozen times. You bring your strength against theirs. Our best unit against their best unit with the game on the line, no screwing around. If you think you can scheme the run game open maybe you use them for one down, but if Shannan could have done that he would have done so long before the closing minutes of the 4th. So if you don't have the meat at RB to attack a top notch front 7, and don't have the personnel or a good plan to scheme your RBs free, it's foolish to force it, especially against a team with momentum. Go with what got you there. And what got the Falcons to 51 was Matty Ice.
Frankly what killed the Falcons wasn't Ryan or Freeman or Shanny or any of the usual goats people blame. It was a weakness in the strength and conditioning throughout the team. Bill had the guys put it all in the bank and they had it to spend in the most important 30 minutes of their football lives. The Falcons didn't.
Freeman being put in a blocking position on the strip sack and missing his cue just raises so many red flags. You do NOT put a 200 pound running back in that position unless you have no choice, he's not used to it, and he really doesn't have the meat to pull it off anyway. Especially not liked up directly opposite Hightower in his prime! I can only think they did it because their OL was exhausted and they needed someone, ANYONE, to come in and try to help protect Ryan. Even with that though Freeman was an odd choice.
And the holding call is an exhaustion based error as well IMHO. OLs who are wobbly on their feet due to fatigue will hold if they get beat. In my mind what killed the Falcons was exactly that: strength and conditioning. Front 5 and front 7, we wore out the Falcons, they made mistakes, and we capitalized on them. All because our guys just plain put more in the bank than their guys did.