Zelda historically doesn't sell great actually, it doesn't move the needle in that way. Zelda sold great on Wii (Twilight Princess), but on Gamecube it was low. Granted 1m isn't low, but for a series like this where everyone assumes it sells consoles... that's low. 2014 was the year of kick ass games on the Wii U, Smash always being called a System seller, and none of those games helped sell more Wii U's sadly. I love my Wii U, the games on it are great, but it was a shit storm coming from the Blue Ocean strategy that killed the Wii U, and the fact that it was outdated a year later. Nintendo's unwillingness to go towards Internet based stuff also has not helped. Wii U eShop sales of games only accounts for 8% of their sales, and it's not because people don't want to, it's because it sucks. I have an external drive plugged in to my 32GB Wii U because 32GB is a joke. Xenoblade Chronicles X, assuming the Wii U had nothing else on it, would fill the entire system.
Nintendo lost 3rd party at Gamecube, only had some 3rd party support in Wii because of the gigantic install base but NO ONE talks about the Wii ports of anything and we obviously ignore all the shovel ware, so they didn't retain them for the Wii U.