The Wii itself alienated most Wii owners, so they abandoned it. Developers that aren't named nintendo abandoned it long ago. They lost all momentum and tanked 2 years ago. What they pulled off in the first few years was amazing, what its been for the last 2 has been a total catastrophe.
The rub with the Wii U is that its not going to be a next gen system. Its just a really late entry into the current gen. That trick worked once with a great gimmick for a short period of time, but their gimmick this go round just isn't going to cut it. The Wii U could have been a reasonable success a few years ago, maintaining some of the momentum they had left. That momentum is gone. And now the industry is getting ready to move on from ps3/360, and their new console is going to be instantaneously obsolete and left in the dust. They're already seriously "out of position", and the Wii U isn't going to cure that.
Ive always been a big fan of nintendo, but their strategy of bottom feeding is ultimately going to be their demise. They haven't kept up, and now they're so far behind, I don't know what its going to take for them to catch up. Even if its a moderate financial success, and thats the best case scenario, they've long ceased to be the industry leader in the eyes of gamers. They're not even in the same league anymore.