Obvious answer: no more game released on Switch 1 so you want a Switch 2 if you want to play new games.
That's work well enough for Playstation/Xbox.
The difference with the other consoles mentioned is that it's portable, and the time already made clear (with Switch 1 and Steam Deck) there is a massive need.
Clearly it's the same basic platform. And I think that's fine - they've really cornered a pretty big niche of mobile (ish), motion controls, family.
I suspect the larger screen size is because more people are using the mobile aspect in their home, not out on the subway or something.
This is obviously more of a teaser than an actual full trailer.
They announced a Nintendo Direct on Feb 2, so I’m sure full/most details will be covered then.
In a couple years we'll have a new console war between Switch 2, Steamdeck 2, and Xbox portable.
This is where your first point is critical. People who want to play Mario/Zelda/Pokemon etc will buy the console, regardless of form factor.
Im sure there are more details in this video for someone more discerning, too. My point is that I didn't find there to be much information in the trailer because it's clearly mostly a refresh. And I'm not complaining about that. Nor am I complaining about the nature of teasers.