I don't thinks it's quite that simple, there are other factors as well:

There are significant network effects. Content creators use youtube because there are a lot of viewers watching content there, and viewers use it because there is lots of content there. Since YouTube already dominates the market, it is extremely difficult for another platform to compete, even if it was better in every way.

Google can promote YouTube using its other monopolies/oligopolies. Most notably, google search prioritizes videos on YouTube over other videos. Also, being able to pay for video ads and search ads with a single vendor is probably actractive for ad space buyers.

Google also already has its own CDN, which probably reduces the cost of distributing the content.