Social proof is a major aspect of all social metrics, including YouTube views. It basically looks at how group actions impact an individual. On YouTube this means that:
A video with very few views has little social proof, and is ignored easily.
This is why so many new YouTube channels struggle for so long. They get stuck in a rut because they lack social proof.
A video with lots of views has more social proof, and is able to get more views because of this.
YouTube users believe it to be good based on its view count. This is how videos go viral.
We have all seen a video and, without knowing anything about it, clicked on it purely because it had so many views. There’s probably also been time where you have seen a video matching a search of yours, only to ignore it for one that has more views. In both instances you were impacted by social proof, and they both show that it is very real on either end of the spectrum.