I think MB had a problem. Ethan is a natural introvert (odd for a professional athlete, but he's an introvert none the less). This is a problem for MB because good Television is almost all about A type personalities.
Because Ethan is an introvert, there was almost certainly little in the way of footage that could be used to build a compelling character or story around him.
Ethan didn't initiate the winning alliance.
Ethan didn't perform well in the individual challenges.
Ethan wasn't one of the 3 "fish out of water" in the switch.
Ethan didn't initiate strategies.
Ethan didn't cultivate close relationships.
So MB had a problem in that the winner of SURVIVOR was pretty much... boring.
There wasn't anything MB could do once the film was in the can, so MB editted the interesting players like Lex, Lindsey, Silas, Tom & Kelly into the show to pull viewers in, but editted them as evil or idiots so we wouldn't be upset, and maybe we would be pleased that they didn't win.
MB then had to edit the show so the person whom Ethan faced the jury against wasn't more likeable Ethan was. Thus, MammaKim got little face time or development in the show.