I didn’t say it was a complete fluke, I said it was an outlier. Imagine you're running Nintendo, you're making great games but every generation of home console sells less than the one before it. The trend is going in the wrong direction, and below some number, it doesn't make sense to keep making consoles. The Wii changed strategies and it paid off big time. But the trend didn't last. They tried to build on Wii with Wii U, but that sold even less than the GameCube. I don't think you keep making home-only consoles after Wii U, praying that lightning strikes twice.
All the while, handhelds are still selling strong. There were some ups and downs, but even the worst-selling handheld (3DS at 75m) outsold the best-selling console (NES at 62m).
My point is that they saw where their home console market was going, where their handheld market was, and made a smart move to build a higher-end handheld that could get home console games, handheld games, plus attract indies and regain some 3rd party support.