Edgyhead has Eggyhead's lore, which sucks yeah, but the thing that made him go mad is his curse of knowledge, just simply grasping the knowledge of the universe is enough to break someone, Edgyhead knows the knowledge of a god, which is what makes him so insane.
https://youtu.be/lNoUP579nQ8?si=4oouqhPgjPwo3HAb also I think this song fits him :P