They had a much better data-driven read on demand this time around, and it payed off, literally: they sold nearly 3x the units as the NES classic. They (inadvertently?) manufactured nostalgia demand with that first release and built-to-fulfil with this one.
Moving over 575k units of hardware that's like 26 years old in under half a week is incredibly impressive when you think about how companies like Atari and Sega have been selling digital-running nostalgic consoles in grocery stores and pharmacies for years now at peanut prices.
A rising tide raises all ships and Nintendo is certainly benefiting from a halo effect around their brand lately.
Yea, it's incredibly impressive that they were able to manufacture this kind of hype when so many others have just been doing bundled "classic" packs at value prices with little to moderate success...
I think a big piece of it is bundling in the classic styled box, along with the traditional controllers. The nostalgia packaging is really what drove sales, and I think people being afraid of NOT getting one (ala the NES) led them to really go hard in lines, and Nintendo was ready and actually met the demand (and it's likely still there, and will be through the end of the year).
Kudos to them, my crow was delicious, and my SNES Mini is phenomenal.