They were released simultaneously, Breath of the Wild was a Switch launch title. Same with Twilight Princess (actually I think the Wii version might have launched a few weeks before the Gamecube, I assume that was more to incentivize people to buy a Wii. Not the potential issue here regardless)

Tears of the Kingdom already had its launch and sold a TON of copies. If the new console isn't backwards compatible, they either are going to have to resell it to you which is a big ask, or just not have a new Zelda game available to play on their new system for another 6-7 years, which is not likely.

True, but those came out at the same time, so most people were only buying one of them. Whereas Nintendo just sold 18 million copies of Tears of the Kingdom, so a lot of the expected buyers of a Switch 2 version would probably already have it.