He's introduced as a muscle head with no sense of the long-term consequences of his actions. It changes during the flying exam, but usually shounen manga would lessen or entirely remove that character development for the sake of humor or prolonging the drama. Sabnock actually just... stays true to what he learned from that experience??

It's to the point he gives the same advice to azz in the walterpark arc, and he's more compassionate because being kind is cool! He rarely competes against Iruma — he competes against Azz more actually — and instead has a strong respect for him. Sabnock knows Iruma is a good guy, and rather than being full of jealousy towards him, he likes and believes in Iruma!

This would've been a good moment for Sabnock to "go to the dark side" so to speak because Baal framed Iruma as manipulative. Most stories would disregard the rival's intelligence and development, so they could go against the protagonist except Osamu Nishi doesn't!!!!!