Think about the position he was in. Cain had his head against his rib cage and Werdum had his arm around Cain's neck. They fall to the ground and Cain taps shortly thereafter. Now think about how many times in a fight you see both guys in the same position. The guy on top almost never chokes out the guy on bottom from that. It is attempted in almost every fight, and the odds of the guy with top position, and that headlock, turning it into a submission are very low. The first time Werdum gets in that position, he pulls it off.....that's incredible.