Erwin after a short while of having Kelvin behind talk to him about all sorts of things that were of no interest to him became bored and decided to temporarily tune out. This was a skill he had developed which allowed him to purposely refuse to hear any sound around him. He could block out all sounds and just listen to himself talk alone within his head.
"Being me is enough pressure on its own. I have an entire army of friends who are my enemies waiting for the day that I grow weak so they can repay me back for forcing them to see the truth and comprehend what is beyond their reach. Those kids probably think with an elaborate plan, they might stand a chance against me. Well, they would have if Kofo didn't surround himself with idiots. I mean, Max literally ratted him immediately he came to seek my help to fight that oddly powerful boy,"