If you see the video, he was punched behind the left ear which really wrecked his equilibrium and he sort of staggered sideways and was lucky to avoid another overhand right which just grazed the tip of his chin. And still sort of staggering sideways he was trying to square himself up when Cornwall through a kind of shortened left hook which landed right on the button. I don't think that shot caused him to lose consciousness, but because he was squared up he fell straight backwards and his head bounced off the canvas pretty hard.