I think of it like the Stanford Prison Experiment. As a human, we are meant to play roles in a hierarchical structure.
So if I put you in a role, certain parts of your personality are going to come out subconsciously. You become the right person to fit the role.
Pretty much like you said- if you are given wild amounts of money you start to justify it and become someone else.
AFAIK any interaction counts as a plus for the video. Comments, likes, comment likes, subscribes, dislikes, sharing, etc.
Basically youtube’s goal is to make you as engaged with the app as possible. So if a video is causing high engagement, they will promote it more than videos that have low engagement.
It’s all really just complicated statistics handled by machine learning algorithms designed to keep people on the app as long as possible.