John Wick Chapter 2 (still not about the game designer) is a decent example of expanding a one-shot adventure into a campaign. It introduces new enemies and allies, new complications in the setting and John’s backstory, and new spins on some popular beats from the original.
It all makes sense because John has a sketched-in past that’s easy to add more villainous types to, but I’d say it’s a decent example rather than a good one because the way it works is pretty obvious. It also sets up Chapter 3, which looks like it might put John in a less familiar situation, which could help a lot.
(It also runs with the gold coins from the original to suggest various props for Vampire-style boons and debts. Assassins don’t worry about the Masquerade quite as much. And it also takes the setting’s Weird Level just a bit too high for me with one detail of the hitman network it shows, but hey.)