Obviously established franchises have a built in desirability by their fanbase, but I would like to point out that the most wishlisted game on steam right now is a Zombie game that isn't part of an established franchise, may not actually exist, and might not have legal rights to it's own name. The idea that you couldn't sell a game that's not part of an established franchise isn't rooted in historical fact. Even if you look at the Game Award's GOTY for the last 5 years, 3 of them (It Takes 2, Sekiro, Elden Ring) weren't part of established franchises.
New franchises start every day. I get the feeling reading a lot of these documents from regulators that they feel as though nothing new is ever going to be made. And it wasn't that long ago that Sony was publishing games like Infamous. A knock-off super hero game sold well enough to get 2 sequels. Lots of games are essentially IP knock offs of more established IPs. Hell, Call of Duty, along with it's progenitor Medal of Honor Allied Assault were Saving Private Ryan knock offs.
Because Insomniac were mostly work for hire developers that didn't own the art they created. Had they owned Spyro they would have been scooped up by Vivendi years ago. Sony would have likey purchased them earlier if Insomniac owned Ratchet. Ironically, not owning their own work meant that they would never earn residual income from those franchises, affecting them financially, but also made them less attractive for acquisition.