Rudeus could think of nothing but how to get Eris back home, and on top of it he promised to help Ruijerd with the Superd clan's ill reputation. Even when he failed with the death of the kid, he still felt that crushing responsibility on his shoulders. He couldn't afford to show anything more than he did, nor think of anything extra, so he just locked up. I'd say the episode showed perfectly how a person who foolishly accepted a responsibility of immense importance well beyond their means would behave when the house of cards starts collapsing.
But yeah, it's impossible not to like the fight scenes.