One-and-done versions I think will work, but when they start tying supplements to those, such as modules - that's where the real revenue split starts to occur, when you start getting into content that is only being picked up by a fraction of a fraction of your customers.I'm actually very surprised they're suddenly doing so many settings - as noted, one of the big problems faced with TSR was that many if not most people didn't use any published setting and very few used more than one. So they were competing with themselves, turning a potential success into multiple failures. It's a surprise to see WotC doing the same again.
Example: Releasing the Strixhaven campaign setting only picks those with interest in that campaign setting. If the following 5E adventure "Through the Wimbly Woods" is just a 5E adventure, you'll have a fair number pick it up, with perhaps a small percentage being those running a Strixhaven campaign. If, however, the adventure was "Through the Wimbly Woods: A Strixhaven Campaign Adventure", you're only going to pick up people who A) are playing Strixhaven and B) are interested in a megadventure. The customer base will be a fraction of what it could be.