Don't you mean Captain Planet? well the evil doppelgangers is not really new, i mean mostly every cartoon has an evil counterpart of themselves.
Anyway i kinda think it was because Ted Turner was forcing us to watch the cartoon, mostly i hate him when he said this:
"We have more cartoons than anybody: The Flintstones, The Jetsons, the Smurfs, Scooby-Doo. They're nonviolent. We don't have to worry that we're encouraging kids to kill each other - like SOME of the other cartoon programs do"
That's when Swat Kats got canceled, i mean he talks about not worrying about cartoons that have violence so what does Captain Planet has?