If a poster can't comprehend how the biggest game of all time in Japan can move hardware or how a game that appeals to female games can be the main cause of a spike of demand for the Nintendo Switch, I don't think it's worth your time to argue with him.
"Assertions", nope dude it's a game that is going to break all the records by the end of its first calendar year on the market. Comparing this to Splatoon on the Wii U, isn't the aptest comparison because there is actually no comparison for how well New Horizon is doing in a non-holiday quarter or how well Switch is selling compared to Wii U. Although COVID could be a major impact for the video game industry in Europe and North America - in Japan it was a non-factor.
FAMITSU TOP SELLING GAMES JAPAN ALL TIME(physical):
10. Animal Crossing: New Leaf (3DS) - 5.067.988
11. Animal Crossing: New Horizons (Switch) - 4.860.488
12. Monster Hunter Freedom 3 (PSP) - 4.850.000
TOP 15 Switch Famitsu 2020(w/out New Horizon):
- Pokemon Sword / Shield - 632.934
- Ring Fit Adventure - 510.430
- Mario Kart 8 Deluxe - 327.445
- Smash Ultimate - 272.264
- Minecraft - 267.961
- Pokemon Mystery Dungeon: Rescue Team DX - 258.185
- Dr. Kawashima's Brain Training for Nintendo Switch - 212.375
- Super Mario Party - 203.628
- Splatoon 2 - 202.582
- Luigi's Mansion 3 - 147.436
- Super Mario Maker 2 -124.901
- Mario & Sonic at the Olympic Games: Tokyo 2020 - 119.007
- One Piece: Pirate Warriors 4 - 117.954
- The Legend of Zelda: Breath of the Wild - 116.147
- Xenoblade Chronicles: Definitive Edition - 115.525
TOTAL: 3.628.774