I also think the fence aided Shamrock's ability to deliver a knee to the back of the head. He was able to create that angle and leverage with his hips because his right foot was positioned high on the fence. If it had been Pride rules in a ring (you're not allowed to use the ropes also), they would have been put in the middle of the ring, those knees would have been legal but only landed on the side of Renzo's head, not the back of the head. And Renzo could have retaliated in kind.
I don't recall Frank going for one submission attempt while on the bottom. It looked like he was simply trying to neutralize Renzo. At the highest level it takes time to work a submission and Renzo was slowly isolating Frank's arm the first time they were stood up.
I really thought Frank Shamrock was a great fighter until he dropped out of the game when the competition started getting better. He's been out of the fight game for 7 years and claims to be undefeated in 10 years. How do you defend that? If SHAMrock does fight Phil Baroni, he will have his hands full.