Algorithm, Search & Distribution
Cold start
Also called: cold start problem
Recommendation systems run on history, so anything brand new gives them nothing to work with. That is the cold start. It covers the opening hours of an upload, the first weeks of a channel, and the viewer who installed the app this morning and gets broadly popular material until they watch enough for a pattern to form. YouTube judges each upload on how the viewers it reaches respond right now rather than on what the channel managed before, so every video passes through a version of this regardless of who published it.
A quiet first day gets read as a punishment. Most of the time it is the system still working out who to show the thing to.