I'm not sure that the Klingon had really let his history go.
He commanded indiscriminate killing of non combatants in fear has he lost ground. He ran from the battle and took the title of Butcher of J'Gal to hide from his actions, and his front of wisdom was just another way he could hide to preserve his life.
Fear of being exposed as a fraud caused him to lash out against Benga. He died without honor as the coward he is and was.
"Look how he couldn't allow the bad things to go on and turned on his own people to stop them! Much Inspire!"