So essentially, Kanki knew what kind of person Kochou would be: a zealous military general who has been out of action from being promoted and takes this chance to 'punish' a bandit turned general who needed to know his place. So seeing that Kanki was a GG and throws his army in the grinder supports his view and knows he will win because he has a better trained army with high morale and supported by their privileged numbers. But that was all an act to just draw someone like him in and so Kanki sacrificed cowardly bandits to run away to give Kanki the feint he needs to sneak around a overconfident Zhao army who thought he was simply throwing away lives for nothing. He only used the professional soldiers of Qin on the left wing so they can win glory but knew the center and right wing are made of unreliable recruits who needs to run away as intentional bait. What I'm saying, is that Kanki just pulled a 400 iq chad move through playing by his rules as a bandit only with the twist that he was pretending to be incapable and cowardly.