I think the other thing that probably helped Switch the most and is helping Switch 2 is people want portable platforms.
The two systems that are comparable to the Switch in sales are the PS2 (which was also often bought as a DVD player/media entertainment system and had heavy discounts) and Nintendo DS. The 3DS had product launch mistakes which hampered its potential and momentum. If Nintendo launched it well, it probably would've sold more than 100 million, which is fair given it had some competition, even if weak competition. 70-100 million is roughly the baseline for Nintendo handhelds in more recent decades.
The Switch was basically able to capitalize on portable gaming popularity while also being a good home console too and capturing both audiences. It had a great game library as well, and given all of that it is not a surprise it and the Switch 2 are big successes.
As long as a steady stream of games release on these platforms they can sell well by hitting fundamentals.
