Just a guess but because fat Ruiz kept on punching him? Thor went Nordic God on him for two rnds and Ruiz was still punching back. I would quit too.
if that fat boy can get in shape he could be a contender been a while since we seen a heavy throw fast combinations
I was hoping for a better answer than that considering the profession he chose has a strong emphasis in punching your opponents as much and as hard as possible. That was a disgrace to the sport.
All joking aside that is exactly what happened. Thor threw everything at Ruiz and Ruiz didn't fade. Thor saw that he couldn't intimidate this guy and got scared and called it quit. Thor is a quitter when things get tough.
Andy Ruiz, Jr. surprised me a lot. He looks out of shape, but is not. I think he is the best American prospect today.
I'm surprised this hasn't been mentioned. On the stream I watched, when the cameras cut to his corner, he could clearly be heard saying to his trainer (very close to these exact words; the particular video I watched has been removed now), "My legs are gone, I just can't concentrate, I think I partied too much." And then they quit the fight.