Splitcast Technology built this in 2012. The company folded (couldn't find revenue, and had founder struggles ) but as far as I remember the tech worked. It still needed a lot of seeding nodes, but a significant chunk of the bandwidth was provided by the "viewer peers".

Key part of that tech was that it synchronized the playback between all peers. That was nice for stock market announcements and sport events for example.

https://web.archive.org/web/20131208173255/http://splitcast....

https://www.youtube.com/watch?v=R5UYu9jeQbY

https://www.crunchbase.com/organization/splitcast-technology