Was the Wii a fad?

[Mnementh]

Panama said:

Of course not. Anything that sells insanely well initially and then sells less than its two competitors for nearly 2 years straight, then sure i'd qualify it as a fad. I'm honestly surprised people are adamant that the Wii wasn't a fad when the PS3 and 360 hammer it sales every week now. People are aware the 360 is one year older than it right?

That's the point here. The Wii destroyed the competition early in the gen, but now is outselled by nearly the same percentage. You can say, that's because the successor is already on it's way, but that leaves the question: Why does NIntendo bring the successor so early, if they could have made money on the Wii otherwise?