Explanation
Because the seed audience is small, the metrics that matter most in the first hour are the ones that move fastest: whether people watched past the opening, whether they engaged, and whether they rewatched. Comment activity in that window has an outsized effect, which is why replying quickly is mechanics rather than manners.
It also means a genuinely good video can fail. If the seed audience was a poor match for the subject, strong retention on a tiny sample never gets the chance to compound, which is the most common explanation for a post that looks fine on every metric and got no views.
The common mistake
Deleting and reposting a video that underperformed. The second attempt gets a fresh seed and usually a smaller one, and repeated deletion is itself read as a negative signal.