Counterpoint: you can have a million subscribers on YouTube, or be the most popular writer of web serials (Wildbow), and not make much money at all.
For a youtuber that might be 1000 people paying $8-$9 a month on patreon.
If you have a million subscribers but don’t have that, then by definition you don’t have 1000 true fans.
People read and listen to lots of people and things, but only deeply, deeply care about a fraction of them. That’s a true fan.
That is one issue with the article: it glosses over the difficulty in acquiring a ‘true’ fan. But, it does show that it isn’t some unfathomable number. Thus better to optimize for being loved by some rather than gathering mild interest from many.
Add in merch, Patreon, etc. and you're balling.