Honestly, they didn't fail for me. I'm the proud new owner of a Wii U, courtesy of the Skylanders bundle I got for $220. Admittedly this is more because my 5 year old had it at the very top of his Christmas list, and when his requests line up with my own desires, it's kind of a done deal.
Two other notes before I get to my real point. Skylanders is awesome, and I'm surprised at the quality of the game itself. Swap Force is my first foray, and I already have the new figure fever thanks to it. And Super Mario 3D World is incredible. Now back to failure.
For a system trying to make gains, the Holiday Bundle is often a real winner. Think back to the 2009 PS3 Holiday Bundles, for instance. There were different variants for each store, and each one had KILLER games along with the newly releases "Slim" 120GB system. One bundle had Infamous and Uncharted, another had Infamous and Killzone 2, I personally picked up the Walmart bundle that had Batman Arkham Asylum, Infamous AND the Dark Knight Bluray.
This is the kind of push the Wii U needed to compete this year. If they weren't going to slash the price for holiday, they needed some amazing bundles. But the fact is I looked all season for a Wii U, looking for a great bundle and didn't find it. The Black Friday offers were tepid at best. Free gift cards, free Wiimotes, stuff like that. Imagine a $249 bundle with the two Mario U games AND Wind Waker?
So why didn't Nintendo come out swinging this past holiday? Did they just think 3D World would drive demand, along with the lower price compared to the PS4 and XBox One? We may never know.