I believe it works like Bittorent (and things like Windows updates) where there is a swarm of peers that simultaneously upload and download to/from eachother, so the original creator, or any single user, doesn't necessarily need much bandwidth. There are some disadvantages to this, but it is manageable, and works for many other things. If it actually became a thing, I imagine sponsored/patreon-funded creators would pay someone to seed their videos to ensure availability and quality. Fans would probably help too. Technically, it's a viable option.

But yeah, with how walled-garden the Internet has become, it probably won't become popular without massive amounts of marketing and doing things like signing exclusivity deals with popular creators, which needs a lot of money.