It’s a cookie clicker type game that occasionally drops steam items that you can sell on the marketplace for real money. Most of the playtime comes from bots, not actual players, which is why it is so far up the charts
The whole thing is a scam basically
Just because the cartridge slot is compatible with old Switch games doesn’t necessarily mean they can’t use a different communication protocol for the new cartridges to prevent them from getting dumped
In fact, that is almost guaranteed to be the case, because otherwise the Switch 2 would be launching with a flashcard available for it on day 1.