How did people find his unreleased stuff?

I recently switched from Spotify to YouTube Music and discovered a bunch THD tracks that were reuploaded by fans. I'm a new listener, so I'm wondering if there's any back ups? There's only a handful of accounts archiving these tracks. And I'm also wondering where people even found these? Did THD upload them and then take them down? Were they uploaded to a different platform (like SoundCloud)? If it was just a few songs I wouldn't be so shocked, but there's at least an album's worth of unreleased music from THD, most of it is great stuff too.