Google owns the platform and the ad network / marketplace. A lot of videos ‘lose’ money and just take up space. Any viable competitor to YouTube would need a solution that allows signups, watches and video uploads, without requiring a fee. Which typically means displaying ads. For Google the ad network is already there. For anyone else, they need to either create their own marketplace, or have Google (or some other network) take a large cut of their ad revenue.

This is likely why the only other ‘competitors’ you see are peering based or based on a subscription model. Neither of which can really compete with YouTube which really doesn’t need to *directly* make any money