It's simple, marketing is what killed the Wii U. Such a simple thing as a name probably cost them Billions in sales. They tried to capitalize on the brand name and success of the Wii but it backfired because people thought why should I spend 400-500$ on another Wii? The Wii U was not a mistake. It was a brand new more powerful system that could do everything the Wii could and more. If the Wii was a success, there's no reason to think that the Wii U couldn't either.
Much of the sales of the Switch was carried by the first party heavy hitters like Mario and Zelda. Which games will carry the Switch in 2018? Will we see another Mario and Zelda on the Switch? Every single game in the Zelda franchise has been re-re;leased except for Skyward Sword. Time to re-release that game without the gimmicky controls!
Mario + Rabbids is the only Switch game I'm legit interested in playing. Hear lots of good things about that one.