I really hate to bring this up; but this is exactly what I said would happen in the last chapter. "Absurd Oppai Moment + Cheap Magical Theatrics = Resolution". Literally, go look. I'll wait.
Suggest you all read the WN version, which goes into further detail on the other hero party members and what happened to them after they kicked Dylan out.
Long story short,
they were all awful, selfish people with their own petty, selfish desires for power and glory. None cared for the other, being put together by an alliance of nations more interested in personal political posturing then actually defeating the devil king.