Okay, new (?) Legion theory: the show has been narrated, a la Doc Scratch, by the Shadow King ever since the moment he got his body back.

This explains not only the way SK suddenly becomes a benign side character whose immense powers and psychopathy don’t really worry anyone, but also how the strange rhetoric about “insanity” very recently espoused in an obviously suspect manner by SK-in-Melanie’s-body starts suddenly being adopted by the show itself (as I boggled at here, right after finishing S2)