Another obvious reason as to why flappy bird became popular, is due to how hard it is. Actual challenges provoke emotion and frustration as well as an urge to overcome the difficulty.
Person A: "I can only pass three pipes..."
Person B: "You're obviously shit, let me show you how it's done!" *proceeds to download app*
This is somewhat related to the Food Optimization he mentioned and gaming in general, some people want the chunky sauce (actual challenges) rather than the bland experience.
This leads to what has been fairly obvious for about a decade, that mainstreaming is killing game quality and stifling creative/original content as investors aren't willing to take the risk.
Ironically, those same investors were all too happy to dish out for one MMO disaster after another, which in turn discourages them to invest any further in gaming.
The movie and music industry suffers from the same issue; Mainstreaming and reboots have become the safe option, hence all the terribly bland franchise reboots where effort and creativity is discouraged.
So with all the mainstream games, it's obvious that something that stands out might get a lot of attention.
The trendsetting is an interesting point, but I think my own reasoning is more valid.
Here's why I think so:
As much as we just jump on some bandwagons due to group-mentality, we are also so individualistic that we don't frivolously spend a (relatively)large amount of cash on just anything.
Again, the reason that so many MMO's failed in the footsteps of WoW was that people had already invested their time and money, and weren't willing to take a risk on something new.
Arguably part of it is that they didn't want to abandon their social group in WoW, but honestly if people didn't like the game, why would they stay in the first place?
It seems obvious to me that people don't merely stay because they're lazy or desperate to hang out with their friends in one game. They either stick with it or they don't, depeding on whether they like it or not.
So what about Minecraft, Flappy Bird, Binding of Isaac and other indie titles?
Unlike a brand new console, they're dirt cheap. Some of them cost less than a bag of chips or a trip to the local fastfood joint, meaning that people don't see them as a risky investment at all, especially when there's a following recommending them.
The attention game.
So this is where I somewhat validate the theory of trendsetting and youtubers.
There's a huge investment being put into researching what people want or like, to the point where we're bombarded with these things.
Social media in particular is extremely invasive with this, but I get the feeling that it's also largely ineffective for anything else than the mainstream.
Youtubers are (usually) independants giving out their honest opinions, so people tend to trust them a bit more than say, gaming news websites, when it comes to reviews or gameplay footage.
They are also people who typically know exactly what they want, so I'll more often hear about interesting kickstarters and crowdfunding projects from them than here on the Escapist, for example.
Since I'm subscribed to the people I like and share my interests with, they're more likely to show what I'd like myself, unlike the Escapist which show off projects that gives them the most clicks, such as feminist boardgames or what have you.
My point with all this, and keeping on with the pasta sauce analogy, is that we keep seeing the bland shit on news sites and the more chunky, focused projects don't get attention in the mainstream.
Now youtubers are being monetized and becoming a small industry, so it's going well away from being independant to sponsored content.
Ironically, by seeking more money, the people investing in these channels are stifling new markets/investment opportunities.