He couldn't. He had taken punishment for 9 rounds against one of the P4P hardest punchers in the sport. He was probably exhausted.
It could be a case of the urination effect, as you're still going to get thoroughly drenched even if someone is only trickling on you if they do so for long enough? But personally I just think it was a case of him suffering from acute discombobulatization after that heavy right hand to the temple region which are located on each side of your noggin.
He was taking those shots for 10 rounds. Might look like he was taking them well but he was just been grounded down an when it was more like the accumulation rather than one sudden shot that finally dropped him again. Once that happened it just looked like the mental will an physical strength just drained out of him.