Cartoons got weird.
I remember when it began happening, and I'd argue one of the major touchstones for modern animation in all forms is John Kricfalusi's "Ren & Stimpy." When that show hadn't gone on the air yet, tapes of it were circulation in the animation community in LA, and I remember talking to a great animator named Eddie Fitzgerald about the show. He was positively evangelical. He said that the show was going to change the way animation looked and the sort of animation that would get produced. He had already decided that he was going to quit what he was doing at the time specifically so he could go work for Spumco. He was a true believer, and he wasn't the only animator who sounded that way when talking about that show.