That's because the universe knew it would be ported to PC in no time. Without the PC port this game would've completelly unsustainable.
Instead of learning that exclusives are still viable they'll learn that is better to not make AAA games.
Tell that to Nintendo then, because they are unaware of that and have become market leaders, selling the most consoles, the most games and making the most game. Not having to depend on other publishers is a positive thing not a negative like you are suggesting.
Also, don't worry third party publisher will show up for the Switch 2 like never before in a Nintendo platform, brace yourself.