Quoted By:
Amazon Best Seller Ranking™ =/= Raw sales
The ranking is a compound score. You get extra points for brand (Nintendo), money paid to Amazon to appear higher in the list, page views (if you look at the questions, lots of people are complaining about the game, so not all views are from people interested in buying), engagement (again, the questions), etc.
It is described as a "vanity score" by a professional marketing book.