One thing I would suggest: stop looking at viral videos as "bad." You obviously didn't like Harlem Shake or Gangnam Style, but that didn't mean they weren't valuable enough to a lot of people to invest time and credibility in. Maybe they weren't to your taste, but if you go in with the mindset of "these suck, why did they go viral," you aren't going to learn from them. Analysis requires an open mind.
Harlem Shake has two sections: one guy dancing stupid near people not paying attention to him, then all of them dancing. This happens in 30 seconds. It's weird, it involves costumes, and appeals to the "I wouldn't ever do this!" part of western societal training. It actually appeals to shame, if you ask me. The sharer thinks "I personally would feel shame if I did this so watching others do it makes me laugh and feel like I am better than them." In a way, sharing a Harlem Shake video likely started out as a means to laugh at those idiots for doing that stupid thing, then people got in on the joke and it transformed into more of a positive "IDGAF we are doing this!" fad. Then celebs got into it and the same people who shared because they felt better than the people in the video likely were either mad because it caught on or happy because they felt relieved they can also do funny things, because their favorite ____ also does.
Gangnam Style is on the surface, utterly silly. It's a lot of different scenes that don't really appear to have a context. Upon further inspection, you (should) start to realize it is a critique of people who fancy themselves upper class. The lyrics are obviously irrelevant due to being in Korean, and most people not in one of the Koreas don't speak it. There is more to Gangnam Style than meets the eye, though, and I think most people recognize this at very least on a subconscious level. The beat, however, is one that you will remember later, as are the utterly ridiculous scenes like the humping elevator guy. This video, I believe, was shared due to positive sensory overload. So many silly or unfamiliar things happen in the video in a rather short time, it is hard to criticize with anything other than "this sucks." Which isn't a valid criticism, and strengthens fans of something's resolve about liking it. When is the last time someone told you something you like sucks? You probably thought they were a jerk and ended up liking what you like more.