Abandoned series.

[Bramblethorn]

When you write fanfic, you are stealing from THEM, the authors who likely got rich from their work

Citation needed...

There are a few authors who are lucky enough to get very rich off their work, the Rowlings and Kings of the world. You could probably fit most of them in a medium-sized house (egos) not included. There's also about a football stadium's worth of authors who've written stuff people loved enough to write fanfic about, but who are nevertheless poor.

Just as one example: Ao3 has 220 fanfics based on Peter S. Beagle's "The Last Unicorn", not bad for a story that came out in 1968 (film adaptation 1982). It sold over six million copies and shows up on a lot of "most loved fantasy story" lists. But a few years back, one of his friends had to run a fundraiser for him because he couldn't afford to buy groceries. (Combination of a bad deal on the movie - even I know "5% of the net" is terrible - and non-payment of royalties, and apparently fraud/elder abuse by his manager.)

Fandom isn't part of the problem there. I expect some of the same folk who wrote TLU fanfic would've been donating to his fundraiser, or helping get it in front of others who could donate. But let's not pretend most authors are rich.