It was inevitable he'd have to move on. It's like doing a series where the joke is "Yuyuko is a big eater" - you can only get so many punchlines out of it, and after you have her eat a whole island, or Kirby-vacuum a character, you have nowhere else to go that wouldn't be retreading the same joke.
He's warped the 6th DesDiv's personalities so thoroughly by that point he was running out of gags to Flanderize them with. Only thing to do is start over with a new batch of characters.
Why do you even go like that in front of people kuma?That's just normal thinking.It'd be embarrassing to talk honestly...But just looking at it, you're even more embarrassed about it now kuma.No way!?Passable.