The comparison to imgur is interesting, as imgur is itself trying hard to make money now by removing lots of content. The history of image hosting websites is a history filled with image hosts failing for the exact same reason.

This post should be an interesting read:

https://drewdevault.com/2014/10/10/The-profitability-of-onli...

The thing is, there is no way to provide a free content hosting service in the long run (whether image or video)