It's not that easy though. Switch and Wii suceeded for completely different reasons. Wii offered new ways to play and offered the games for that. Switch does offer one new way to play: play seamlessly mobile and at home. But the point here is, that the games haven't to be changed for that. Therefore Switch adds value to any game releasing on it, even if it is ported unchanged. That's why old ports and indies do so well, Switch adds value without the game developer anything at all.
But this was not clear from the presentation back then. The hybrid nature was visible, but it wasn't clear it would add so much value to games, you would have to try for yourself. And therefore it wasn't clear that ports would sell that well, and that resulted in big support. That is why Switch has so many games and 3rd-party support that shapes up to be more substantial than what the Wii had. Back then I didn't even calculated with serious 3rd-party support. But the 3rd-party support changes the image. Think how Switch would look, if support was similar to WiiU. Still a great device for Zelda and Mario - but that's it. That makes a big difference.
You make some very good points. However I want to say the most important thing for any console is the games. A console is just a device you play games on. It's the games that give a console it's worth. However the games at launch and also during the first year set the trend for how the console is going to do.
(referring to bold) In this sense, the Wii and Switch succeeded for the same reason. They both launched with flagship games that people really wanted. New gamers really wanted Wii Sports. Established gamers really wanted Breath of the Wild. Both devices had great flagship games. The Wii U had Nintendoland as its flagship game. People just did not get excited for this game like they did for Wii Sports or BotW. In that sense it should have been clear that the Switch would do well right out of the gate, because it launched with such a great game.
I don't want to negate what you said though. The hybrid nature of the Switch gives it huge advantages. The biggest advantage is that Nintendo always gets good third party support for it's handhelds. They have had problems getting third party support for their home consoles, but not their handhelds. Now they can use all of their strength in the handheld market and bring it to the home console market.
That is why the people who are now guessing only at the 100m mark for Switch are still way undershooting it. The real wave of third party games hasn't hit yet. Third parties need time to make their games and most of them wouldn't have thought about the Switch until after they saw it succeeding. Next year we are going to actually start seeing new third party games for Switch, and in 2020 we will get even more. The Switch is still in its slow phase. Once a large wave of new third party games comes along, then Switch sales are going to move into high gear. (And no I don't mean Western AAA, because those games are overrated anyway.)