It shut down because the admin team didn’t want to do it anymore.

It shut down because the admin team didn't want to do it for free anymore. There were just too many people, too many bad actors for little reward. By charging for access, you manage to both increase the reward and reduce the amount of people, so the whole equation changes significantly.

how does charging for access change anything? The owner could decide they have had enough, walk away, and shut everything down anyway, no?

Sure, but the amount of pain that I get from my ~50 paying customers is infinitely less than the headaches that you'll be getting.