going with the 25-30 million range.
Wii-U had everything going against it:
-The Wii name (confused the hell out of people thinking its an addon to the wii and not a console of its own)
-long droughts of major releases
-Released at the tail end of the 7th generation console cycle.
-specs competitive with the 7th generation, but obliterated by the 8th gen. (do I have the generations correct?)
-Gimmick touchpad controller that like the original motion controls, no one knew how to utilize in a fun and unique way.
-still primitive online infrastructure
-Lack of storage space.
With the Switch we still have a power deficit but it looks like they're just completely disregarding anything wii/wii-U related and starting from scratch.
Plus its not super gimmicky, its got motion controllers (which is more or less the norm now) but other than that theres no real need to 'experience a new and different way to play' since its basically just a dockable handheld.
I see it as Nintendo's return to relevance. But not a return to dominance.