It brought the wand controller into the game, which brought us PS3 Move and X-Box Kinect.
But once the playing field was equal, the industry was down to which console could replace your home theater and cable/streaming box. (With PS3 offering 3D Blu-ray and X-Box One throwing hints about cable-readiness.) And at that point, Nintendo needed to get their heads out of the Game.
The image was constantly on young parents, kids, and adults, doing exercise games, which made it the mainstream Console For Your Parents.
Sort of like when the color handhelds took off in the early 90's, the old green Gameboy suddenly started pitching its ads to execs and thirtysomethings to play on the bus commutes. When a Nintendo retires, it goes to the Old Folks' Home.