> other frameworks like Next.js, Rails, Django, etc.

I think that's the biggest difference. Gatsby spits out a bunch of html and js files that can be served anywhere. No database migrations, impossible for someone to install malware on your site, no server costs (static site hosts are multiple and free).

That's the big value prop to me. Hosting is simple, dev tools are familiar (npm and react), plus I don't have to mess with webpack.

(I agree that I have no clue how they'll make money, but I do really like their existing ecosystem).