My speculation is that Nintendo released the Wii U in haste because the Wii had been hacked. Piracy is what killed the Dreamcast, causing Sega to suddenly pull the plug at the height of its popularity. Therefore Nintendo threw something together that would combine everything that was good about the Wii with a bunch of other features that would try to win gamers back from Sony/Microsoft, and didn't have time to do adequate market research first. Just for good measure, take down the WiiConnect24 server almost immediately after Wii U launch to basically force their fan base to "upgrade."
Of course, the reason big-budget third party developers weren't interested in cross-porting their games to Nintendo had mainly to do with the fact it would have inflated their development costs for a limited market segment, since Nintendo hardware tended to be proprietary. So Nintendo throws so much of their launch budget at developers like Warner Bros. Interactive and Activision, practically begging them to port some of their more popular titles so they can have something to advertise before launch.
I had realized the writing was on the wall for Wii U when GameStop released their Holiday 2013 catalog, and everything was devoted to Playstation 4 and Xbox One until page 24, where there were a mere two pages for Wii U and 3DS, just before the Preowned section. I asked a GameStop employee about it, and he said Nintendo just didn't allocate much money to advertise through GameStop. Maybe because they knew they had a monstrosity on their hands, or because they blew too much of their advertising budget from earlier.