A shame all that effort was wasted; you clearly misread the title of the class to be “YouTube marketing”
The first thing you need to know about marketing on YouTube is that everything you know about marketing mainstream products either doesn’t apply or needs to be modified. PewDiePies channel, on paper, using traditional marketing knowledge, should not succeed. Neither should xQc succeed on Twitch. And yet they are both immensely popular. On the other hand, there are many other YouTubers with just a few tens of thousands or a hundred thousand (small in their niche) that should theoretically have millions.
Also, at risk of sounding discriminatory, I must say that I don’t tend to take the knowledge of a 13 year old to be expert level unless they have a proven track record of being far above the average intelligence/maturity level for their age.
Either way though, you’re making the wrong base-level assumption by thinking that everything that applies to typical product marketing also applies to growing an internet audience via a platform like YouTube.