If Bigfoot were a smaller fighter Fedor would have been able to get away from him when he was being pressed against the cage. He would have also been able to reverse the trip takedown and throw Silva's legs aside easier when he had top position. He would have also been able to buck Silva when he was mounted.
While Silva had great technique and control, it was ultimately his size that allowed him to maintain those positions. If Bigfoot were 250lbs in the fight instead of 280lbs, it would have been a completely different story in my opinion. With solid technique and control a big guy can cause all kinds of trouble for someone more skilled but smaller. Brett Rogers had terrible technique but he was able to control Fedor against the cage as well as sweep and mount him. Bigfoot has much better technique than Rogers, yes, but his size is what really did the most damage. The combination of grinding Fedor out on the fence and then maintaining chest-to-chest like Brock Lesnar did to Frank Mir, is what really kept Fedor still.