Gotta love how streaming torrents through shady debrid and indexing services with Stremio is a smoother experience than what these megacorporations with massive budgets manage to scrape together.
Stremio is (mostly) open source and doesn't cost a penny and AFAIK has no malware. It does sometimes have some ads, about which they are very open about.
Debrid and torrent indexing services are simple websites/APIs with some mostly proprietary hacked together backends. Some of them have subscriptions, but you know what you buy if you subscribe, and many don't even have recurring payments. Someone probably makes some profit out of those, but I'd guess the margins are quite slim, and there's a lot of competition.
There are surely a lot of scams out there too, but I'm quite well aware what my $3 per month buys and I know better what I'm installing or downloading than with any commercial services.
Majority of what's happening underneath is done by the saints of the scene, taking huge risks for zero pay.