There are a couple of reasons as to why I think this video went viral and others enjoy it.
First of all the guy reciting the poem is very honest. We are getting a glimpse into his mind, and how his thoughts pop-up. It is fascinating to observe the utter chaos in his thinking, and how this gives other people who don't suffer from OCD a glimpse as to what that is like.
However, I believe that his portrayal isn't that much different to what happens in my own thoughts. When I observe my thoughts, at times, in fact a lot of times it is utter chaos. I don't have OCD or obsess with germs and other stuff, but I do have some obsessions and attachments, and if I am honest it can get quite as manic as what that guy showed.
So maybe, others find this video beautiful because it puts them in an observer role, where they get to experience what goes on for them as well, but they resist or don't want to admit. It's a breath of fresh air to see someone having the courage, openness and awareness, that they don't have themselves
Eckhart Tolle:
Freeing Yourself From Your Mind
What exactly do you mean by "watching the thinker"?
When someone goes to the doctor and says, "I hear a voice in my head," he or she will most likely be sent to a psychiatrist. The fact is that, in a very similar way, virtually everyone hears a voice, or several voices, in their head all the time: the involuntary thought processes that you don't realize you have the power to stop. Continuous monologues or dialogues.
You have probably come across "mad" people in the street incessantly talking or muttering to themselves. Well, that's not much different from what you and all other "normal" people do, except that you don't do it out loud. The voice comments, speculates, judges, compares, complains, likes, dislikes, and so on. The voice isn't necessarily relevant to the situation you find yourself in at the time; it may be reviving the recent or distant past or rehearsing or imagining possible future situations. Here it often imagines things going wrong and negative outcomes; this is called worry. Sometimes this soundtrack is accompanied by visual images or "mental movies.
TPoN chapter 1, Yanym.