It definitely feels like PC has become "neutral ground" in the gaming industry. You're not really taking away sales or business from your console because majority of those who buy a console either 1) can't afford a gaming PC 2) don't want to deal with the hassle of troubleshooting when needed and prefer a plug-n-play option or 3) that's just where their friends are and are comfortable with that ecosystem and love the console exclusive games.
Even smartphones can play most of Nintendo games. If they release their games on PC their hardware were would decline severely because even a mid level PC would run their AAA titles better than a Switch, essentially rendering the points 1) and 2) irrelevant and the point 3 will follow suit once the hardware sales decline
Nintendo would turn into a third party studio after a few years.
Personally speaking I would love to see Nintendo bankrupting and going into a third part publisher for PCs, but it's not realistic. They are too big, have a monopoly of portable market and an even deeper monopoly of japanese market. Currently I can see them releasing a Switch 2 with no hardware upgrades and still selling 20 million+ in Japan as long they keep their first party exclusive