While MaMahon didn’t start the game, he had also not played in the Bears three games before they played the Dolphins and the Bears won all three of those games without McMahon.Doubtful. They were missing some guys, including McMahon for that regular season match.
I also think it was their "destiny" to win the Championship that year.
The Bears defense was intact for the game and yet the Dolphins still put up 38 points against the Bears defense.
The Bears were an excellent team in 1985 and they deserved to win the SB but I’m sure they were very happy they didn’t have to face Marino and the Dolphins offense in the SB that year.
I have no idea if the Dolphins would have beat the Bears in the SB but they would have given the Bears a much tougher games than the Patriots did in the 1986 SB.