The sales reflect the state of the Wii market more than SS as a commercial failure or success.
While I don't doubt that there were quite a few former Wii owners who actually bought or borrowed another Wii to play SS, the reality is SS was released in the late twilight years of the Wii, after it had lost most of its relevance.
Still, it just goes to show despite all that SS had going against it (late cycle release on a dead/dying platform, mediocre Zelda game, questionable art direction, motion plus controls), it still sold 3 million copies and will serve as a very respectable capstone for significant games on the Wii.







