N64 was ing awesome.
But here's my theory. Young adults end up getting married and having a kid(s). Buying a Nintendo Wii or Switch (or whatever) is an easy way to justify buying a video game system.
"Honey, it's for the kids". And most dads don't play so many video games that there will be enough good games on any of the Nintendo platforms.
And keeping Mario and Zelda around means that when this next generation of kids grows up, they'll buy their kids some kind of Nintendo product.