In recent years Nintendo has acquired a reputation as a company that caters entirely to children. They'd become the Disney of gaming — a company that is widely beloved, but only for the nostalgia they instill in those who grew up with their games. For the here and now gamers wanted more "adult" titles. Blood, guts, nudity; these are what gamers craved and Nintendo simply refused to capitulate to the growing tide of "mature gamers" and their desire for "mature games."
If I were to teach a university course on the game industry's response to the desires of its customers — Marketing Via Master Chief 101 maybe — Kirby's Epic Yarn would be the cornerstone of a three-week-long section dubbed "Ignoring Industry Trends And Getting Away With It."