I think you have to credit their influence more than their play, though both played an important role in the victory. Brady looked like a rested and well prepared version of himself at home against the Chargers, but the next couple of games were progressively unkind. I think Brees faded at the end too. Father time may be catching them both, though Brady is a year farther down that road.
Most boring game I can remember, SB wise, though I credit Bill with doing a heck of a job coaching and scheming.
I don't even think it was all that difficult. He knew that the Rams defense was undersized, and so they needed to make sure they made the Rams pay for that deficiency somehow. There's obvious ways to do that, when you have a strong offensive line, so long as you don't fall far behind them in points, which NE never did. You just keep getting first downs. Points don't even matter because you'll get them later, so long as you get yards and first downs, you make them pay for being undersized, a penalty that they can't afford to pay all game long, unlike a rightly sized defense, which could keep paying the penalty all game long, you don't play against that defense the same way as against the Rams. The strategy is very easy and guaranteed to work if you don't fall behind them in points, and NE never did. By the fourth quarter, the Rams defense was dead on their feet, compared to how they started the game. They gave up first downs easier, and eventually points. You could see them crumbling, and the game swirling away from them ultimately, and it was due to Belichick's scheme, but it did not take genius to devise that scheme, but it did require a bit of a genius to thwart it, and apparently McVay's not.