Lol Brock Lesnar didnt join the Marines or something and went to Afghan where he watched bodies being blown apart and watched his best friend die right in front off him bleeding to death because the bottom half of his body is missing.
He just trained Mixed Martial Arts....
There is no Adjusting there. Brock Lesnar has been a dick for a very long time and even before MMA admitted that he likes the feeling off using his physical prowess and just showing dominance over other males.
Brock Lesnar has always been hot tempered and never did care about getting in a fight. The fact that he now actually KNOWS how to fight just means he is a bigger and better bully.
He struggled with adjusting back into the ring though. In his first fight he split Cena's head the fuk opened with an elbow from "fake" GnP.