Some adults have been watching it since before they were in cases of longer running shows. Or just adults getting interested in what the children are.

well with the creator and one of the story writers gone the quality changed along with the direction. Alot of people aren't fans of the last couple seasons. especially the relation shipping nonsense. People were more interested in fiona and cake or marcelines episodes which is pretty telling of what they think of…

yeah they repeatedly threw cj under that bus. poor thomas was even more sad. though at least they brought him back for one episode. cj hasn't been seen since.

Doesn't help that the writers aren't consistent with it. You get over arching plot episodes and then random ones spread inbetween. Identity crisis if you will. You have people in the one camp that just want monster fight of the week and then people in the other camp that are there for the story.
And like you said…