My favorite videogame in my family is wii u, because of Yoshi, Rayman legends(murphy) nintenfo land and wii party u. OK, hard to say, because I am my family are other out of the curve who also loved wii u more than other console.
But I have some guesses why wii u failure.

It came too late, it should have being released in 2011. No gamepad for now. Just pro controller and wii mote + inside. And Zelda SSHD released same day as wii version(the hype for playing the best version would drive initial sales) . Wii sports club complete with physical release(or bundled). 200$ to 250$. All 2012 third party. No excuses developers say:'Idk what to do with gamepad', because it still doesn't exist to worry about . Keep talking to developers and bringing the games we got on wii u in 2012 and 2013, make things happen(lots games were ready but didn't release... Gtav almost. Nintendo shouldn't had to loose these key games

For now, it would get 2011, 2012 and 2013 games, still gets the wii public, and nintendish with Zelda SSHD. And a 200$ price point without the expensive gamepad. Would have much better start than what wii u was. Imagine a 250$ GTA WII U bundle? Lots bought a console only for gta, great part would buy the cheaper one. That would help the momentum, as the same players got gta, would get also other third party games. They ll continue to develop. So, third party would still be alive on wii u while ps360 still get them.
In 2013, introduce also gamepad, sold separately or with wii u in a more expensive bundle (300$). Now with games that use it: zombie u, Nintendo land, Ray legends. Then keep the schedule with wii party, mk8, smash, splatoon, bayonets, he, xenoblade, Zelda to, star fox, pokken. But in way better data planning. Also,all third parties until 2015 for droughts. Set to kill it in 2016 holidays along with switch launch.

Because of all the emulators, duh. Why buy the console when you can just emulate it.

Personally for me I wasn't done with the Wii so I never bought it. After a few years I lost interest and just invested my money on the 360 then onto the PS4.

Honestly it had to do with their insane desire to stick to the God awful PowerPC chip. Such a pathetic CPU could never had compliment the honest to goodness masterwork they had in the form of their dual GPU setup.

The system wasn't at all as bad as we were told, outside that awful PowerPC set up. It made the system entirely unable to even reproduce lower end versions of games released everywhere else. That on top of the worst marketing out there since New Coke Nintendo turned a money printing brand in the Wii into a joke no one was laughing at.

I meant the launch ps3 typo. The WiiU launched against the ps3 and 360 slim consoles, which ofcourse had huge libraries by that time. Maybe in combination with the name and the relatively weak power it wasn't seen as the start of a new gen, leading to even more of a struggle as the ps4 pro and Scorpio are facing now. Perhaps WiiU was indeed seen as an expensive add-on for a slightly better experience.

Btw the Switch cost me more than the WiiU deluxe did (thanks to conversion rates). It was the same price as I paid for ps4 at launch. I don't know how well it sells in Canada to check if price has any effect. To compare Switch CAD 400, ps4 slim CAD 350, ps4 Pro CAD 500, XBox One S CAD 380. Switch is pretty expensive here again, same as when WiiU launched. I found a price of $270 for ps3 slim in 2012, so $300 and $350 for WiiU wasn't that different of a situation.

Switch is pretty weak power wise too, so I guess it's mostly the name and that a handheld makes more sense than a tablet. Ofcourse the jury is still out what's going to happen to the Switch this holiday. Mario Oddessey and Splatoon 2 better deliver.

Awful concept and marketing plus awful name

what are you talking about? the switch is not a replacement for the wii u so dont assume that the console has failed, because it hasn't. Just wait for the E3 to see the amazing lineup Nintendo has come up with for wii u owners only.

Basically this, I would just add no system sellers games in 1st year and huge droughts. Console itself wasnt bad, but everything around console was terible (name, marketing, launch and 1st year lineup, price, software droughts...).

The hardware of the console was outdated and pretty crappy. It was pretty expensive and only $50 cheaper than the PS4 even though the latter had a much bigger library and offered way more value. The only reason it did manage to sell close to 15 million units was because of exclusives.

The market changed and the Wii U didn't reflect that change.