Pretty much this.
I'd say if either 3d world, mk8, smash 4, or Splatoon (splatoon that early could have LITERALLY made the ps4 crash and burn inJapann) came out by holiday 2013 it would have done SOOO much better.
3D World did come out by holiday 2013. It came out in November 2013. But that was still too late. Once the launch window passes Wii U had practically nothing for about 6 months. The biggest exclusive between January and summer was Lego City Undercover. There was also an HD version of the Wii's monster hunter game which had its own 3DS version at the same time. But this wasn't anywhere near enough.