I give up, you are completely unwilling to see sense here.
The new switch is rumoured for early next year, not 2022. It is unlikely that a new MK is coming out soon because MK 9 would likely not reach its full sales potential on switch, 8 and 9 would hurt each other.
First of all I never said AC will sell 50 million. I don't get the logic here, why does AC selling insanely well mean other games will as well. Here's an example, on the Wii MK sold way beyond what any MK had ever sold before, but Zelda sales didn't change and 3d mario didn't see any boost. Just because AC performs well doesn't mean anything for any other game. 30 million sales can't be just attributed to covid boost. If that were the case then all other new releases this year should have sold way more then they have.
Spiderman charted in November because miles morales released not despite. This is common that sequels boost the previous game for a couple of weeks. It happened with TLOU, it happened with new leaf. Typically software sales take a massive hit after a new console releases. Stuff like TLOU 2, GoT and cyberpunk will sell alright for awhile because they are new games.
Launching in 2022 is not "soon." Also, what makes you think MK9 sales would suffer from MK8, a game that released back in 2014 on the WiiU? MK9 can sell 30+ million on the Switch & can be ported to the next Nintendo console. Even the best case scenario for MK8, where it sells another 20 Million, would still be less money for Nintendo than MK9 selling 25+ Million. As for the example of MK Wii, that's not a good one, considering MK DS already pushed the franchise to new heights, and came before the Wii version.
COVID played a huge role as to why Animal Crossing blew up. Its boost can be seen across the board. For Nintendo, their older titles sold millions in a single quarter & broke tons of hardware records. Sony made about a billion in profit in a single quarter in a non holiday quarter. IIRC even Microsoft saw a lot more engagement in their ecosystem. At one point in time, the PS4/Xbox One were sold out, in a year where their successors are on the way. All of the above happened in non holiday quarters. That certainly isn't typical.
I won't be able to convince you about SM selling an extra 5+ Million on the PS4, or that 120+ Million users won't completely abandon the PS4 because the PS5 is out, so I will say that time will tell who's right. Though to be quite frank, a lot of Nintendo fans didn't expect Spiderman or God of War to hit 20+ Million, yet alone do it in two years time.