What didn't go wrong would be the better question, it's probably the single most horribly conceived, designed, and marketed console from any major manufacturer ever and the fact it sold 13 million at all is a testament to the power of Nintendo's IPs to sell even a completely undesirable product to an extent.

As to the hardware power debate, power is just one of many things consumers consider when judging whether a product is good value. It's a factor, but it's not the not the be-all end-all. If it was, systems like the PS2, DS, and Wii wouldn't have comfortably outsold their rivals.

The Wii for example was weak, but it was still a great value proposition because it offered a fun, novel and accessible controller interface and hugely desirable software. The value of the gameplay experience it offered outweighed its lackluster processing muscle.

Great post, I agree with most of it, but the PS2 was the most powerful console ever made by the time it was released. The GC and  the Xbox were more powerful, but the PS2 had a very big head start over them. Part of Sony's marketing schtick back in when the PS2 was announced was its horsepower in order to undermine the Dreamcast. Power is a factor it wasn't the only nail on the Wii U's coffin as explained, but it contributed to its demise.

So much this. I want to add: not only many games didn't support Wiimotes, theres was no package of WiiU with Wiimotes included and a dedicated motion control game came only somewhat later with Wii Sports Club. Which was a HD-port of Wii Sports and was packaged in small chunks and only sold digital. Wii Sports Club at launch and a package of WiiU with Wiimotes or of Sports Club with Wiimotes (and yes, Sports Club as physical game) would've made a major difference. Not Wii-level of success, for that the WiiU was too different. But probably at least double as much hardware sales - which would've also lead to better software sales.

I want to underline this point. Nintendo had a deal with the release of Mario Kart, that with the purchase of MK8 you got another top line game released before (I had already bought most of them, so I got Sonic out of this deal). The WiiU hardware sales were much elevated (I think doubled or so) for months. Many will argue it's the deal. But I say if MK8 hadn't been a great game, the deal would've gone mostly ignored or only had sold to people already owning a WiiU. So it really mattered for hardware sales that MK8 was a great game, although the effect was strengthened by the great deal. But WiiU had not much more. Splatoon and Mario maker were great games, but they came too late. The WiiU would've needed at least two of these games in the first year. Instead they banked all on NSMBU. Even Pikmin 3 (not a system seller in itself) came only about a year later. That was not enough.

Luckily enough, the demise of the WiiU paved the way for Switch. Splatoon and Mario Maker were made in an effort to make the WiiU more appealing, and now they are contributing factors of the success of the Switch. Mario Kart became one of the main selling points of Switch.

And to contrast this even more: Switch had four big sellers in the first year: Breath of the Wild, Mario Kart 8 Deluxe, Splatoon 2 and Super Mario Odyssey. But there were more titles, that I think Nintendo might have hoped to bring success: 1-2-Switch (which should've been a pack-in instead of a full-price game) and Arms. Both failed to be system-sellers, although they are still good selling games at over 1 million copies. But the point here is, that Nintendo placed six games which could potentially sell the system into the first year. It didn't matter that not all turned out to get to that potential, enough of them worked. In an alternate world maybe people wouldn't have gone for MK8D as it was a port and bought BOTW on the WiiU. But there were still the other games. Contrast that to the WiiU, which solely relied on NSMBU in it's first year.

The only social network that ever worked for me. Because it was focused on one topic: gaming. I could plop a screenshot of a part of a game I struggled with and ask for advice. I could brag about my achievements. I could talk about how a part of a game was so great. This was cool. It worked directly from the game, I just had to hit the home button, could post and be back in the game.

I am cross with Nintendo that they killed Miiverse (couldn't have cost the world to maintain it) and I am shocked Nintendo has to this day not offered a way to message friends on Switch. This is embarrassing.

A bit biased aren't we? Last I heard the PS4 sold over 100 million units...and remains selling strongly on a weekly basis.

A ton of reasons.

Reason Number One: Marketing. Marketing. Marketing. The Wii and Switch were underpowered, but they have been hits due to marketing. A lot of Wii U ads focused primarily on kids and their parents. Not a good idea. It's ok to show families, but don't make that the bulk of your advertising. The name itself is a marketing thing too. Wii U is a terrible name. And the marketing confusion early on cemented the sentiment that the Wii U was a tablet add-on for the Wii. Obviously, no.

Price. I kind of get why the console launched at $300 and $350. But once it was clear how much it was struggling, Nintendo should've given a massive permanent price cut. Sorry, a Deluxe model (even with a game) for $300 is still a lot of money for a console that is not as capable as the PS4 and Xbox One. Sony has been willing to take losses before to get more hardware out. The Wii U should've been cut to $250 by 2014 to 2015. By the end of its life, it should've been $200.

Wasting the Tablet. No Wii U game could support two tablets. The tablet also drove up the cost. I have to imagine the Tablet would be at least $100 if sold separately.

Missing or Disappointing 1st Party Games: Launching with New Super Mario Bros. U? A game that played it super safe? Disappointing. Giving us a sequel to 3D Land instead of a Super Mario 64-esque game? Disappointing. No main series Animal Crossing game? Disappointing. Rushed Mario Tennis? Disappointing. No exclusive Zelda? Disappointing. Mario Party 10? Ugh. Need I go on?

Very weak third-party support. The Wii U has what many would consider the worst third-party support of any Nintendo platform (excluding Virtual Boy, obviously). The lack of third-party support has to do with the marketing of the Wii U, and that it was hard to develop for. Even though the Wii U is overall more powerful in most ways than the Xbox 360 and PS3, the processing speed is slower. Nintendo shouldn't have compromised here.

I could say more, but I think I've said enough.

I agree. The controller was the reason Nintendo couldn't cut the system's price. They could have, but they would have taken a loss...and Nintendo is very wary of losing money on Hardware sold.

Launching with nsmbu was a great idea and a terrible idea.

Great because the other games in the series sold insanely well. Terrible because, by the time the Wii U had launched, they had already milked the franchise dry. By the time we had a DS game, a Wii game, and a 3DS game, the idea of "A new 2D Mario game" wasn't even slightly exciting anymore.

What went wrong with the Wii U? In hindsight its really simple. Average Joe thought the Wii U was a mid gen upgrade. This is why the Switch took off so FAST. Average Joe knew the Switch was a NEW console the moment it was announced.