What percentage of Wii U owners bought ZombiU? Ultimately that would determine if Ubisoft or Nintendo deserves the blame. A high percentage would mean that the game sold well within the Wii U userbase and was restricted by low console sales, which would be Nintendo's responsibility.
Zombies are very common in entertain these days. I'm sure the suits look at that and think "Zombies are the hot thing right now! We need to make a zombie game" and figure that that familiarity is the key to a certain hit. I never for a second gave the slightest **** about ZombiU and it was precisely because zombies are the hot thing right now. I'm sick of zombies! I could wait at least a decade before I would have the slightest interest in zombies again. And Capcom alone already nailed zombies in videogames TWICE with both Resident Evil and Dead Rising and then you also have games like Left 4 Dead and Dead Space. There is no need to experience zombies in a videogame setting. It has been done. That itch has been scratched. Ubisoft was really entering a saturated market. The subject matter is so commonplace right now that it makes it harder to stand out. Going with what's hot ironically makes the game less visible than something out-of-nowhere would have.
I haven't bought a Wii U because it feels like it offers nothing new that other consoles with years under their belt have not already done. That also applies for third party games. What does ZombiU truly offer that numerous other games, on platforms I've already owned for years, don't? While I don't consider it Ubisoft's responsibility to sell Wii U's, they didn't release anything that would. They didn't help themselves and pretty much relied on Nintendo to attract the userbase. Again, that is mostly Nintendo's responsibility, but some third parties take that sort of thing into their own hands for their own benefit and Ubisoft did not.