Shadows of Erdtree deserved more sales

This comes with the full game. The DLC itself sold much more 

I get that. Still thinking it deserves much more sales

Why? You expected people to just buy the full game again or they waited for the DLC to buy the game?

Second option mostly. The base game did well selling over 1 million copies (PC and digital sales included) but I think this a Game of Generation, so it deserved a bit more sales and I was hoping the DLC and better PS5 stock could attract new players who skipped the base game 

At this point, there probably just aren't that many prospective buyers left in Japan who don't already have a Switch; it's well and truly nearing saturation.

With Japan's declining population, I wonder if any other system will ever outsell it.

Must be a typo but the base game sold more than 1 million copies. Last I heard it was over 20 million sold

He's probably talking about Japan only

To be fair if you watched the direct you probably have a switch already 

It's not just watching it. It caused some positive buzz for Nintendo on social media so a lot of people who didn't watch it will have come across things about it and been reminded about the Switch.