How did The Grim Adventures of Billy and Mandy go from being a genuine horror show to being proto-Fanboy and Chum Chum?

>inb4 "hurrrr it was never a horror show"
Billy and Mandy frequently went into full-blown Courage territory in the Grim & Evil years.
https://www.youtube.com/watch?v=9rSrRsfHPpk
https://www.youtube.com/watch?v=tZ0P4ArZ7GI

How did this go from being a genuine horror show to being proto-Chowder?