It hasn't had a single month aligned where it didn't sell significantly better than the Wii U in the US, in Europe, and Globally.
And that's WITH stiff as fuck competition from the PS4 the Wii U didn't have to deal with early on. Microsoft also has done the legwork for good relations with 3rd parties and has a console strong enough that it can always leach a port off the latest PS4 game at lower resolution if it comes down to it. The Wii U is too weak to even do that, and Nintendo has infamously shit on every third party under the sun in every conceivable way.
Karma's a bitch.