Well, Ubisoft did a terrible job of advertising and, most importantly for Wii games, selling the game to retailers. Ive been to about 5 different stores that stock Wii games, and only in 1 Gamestop did i find a copy (a lone copy on a bottom shelf, somthing a casual gamer would have missed). Ubisoft did a poor job with the original also, but at least that game had more non-television ads.
Also, Marvolous has little to do with NA sales of either game (NMH1 or 2), which is where the original sold best. Its easy to say that the game tanked if you count the JPN numbers only.