First off I applaud the fact the Flat Earthers' are actually employing Cartesian doubt, a method of skeptical thinking following a philosophical idea that the world outside the self is subject to uncertainty initially promulgated by René Descartes, the French philosopher, mathematician, and scientist.
Next consider Michel Foucault, a 20th century philosopher who made a career of studying those on the fringes of society to understand what they could tell us about everyday life.
He looked closely at the close relationship between power and knowledge. He suggested that knowledge is created and used in a way that reinforces the claims to legitimacy of those in power. At the same time, those in power control what is considered to be correct and incorrect knowledge. According to Foucault, there is therefore an intimate and interlinked relationship between power and knowledge.
Consider, for example, the way in which early religious institutions, who previously held a very singular hold over knowledge and morality exercised a very ridged control over that knowledge which then in turn supported their position of power. While that religion based control eventually ended it would seem that today we are moving towards a network of scientific institutions, media monopolies, legal courts, and bureaucratised governments which are replacing those former religious institutions. Foucault argued that these institutions work to maintain their claims to legitimacy by controlling knowledge.
Consider HG Well's "world brain" essays in 1936, that held that a worldwide shared resource of knowledge (such as today's internet) would create peace, harmony and a common interpretation of reality. It appears that quite the opposite has happened. With the increased voice afforded by social media, knowledge has been increasingly decentralized, and competing narratives have emerged each supported by cadres of followers who would never have met nor been able to organize without social media.
So far so good, then it gets scary.
A recent YouGov poll (believe it or not) found that only about two-thirds of Americans aged between 18 and 24 believe that the Earth is round. Furthermore, there seems to be a growing belief that the idea that the Earth is round (well actually an Oblate Spheroid iff'n ya wants to be picky) is actually a conspiracy theory.
And it's gaining more believers than some of the other conspiracies out there, like chemtrails (which, as we all know is actually Chris and his cohorts, dispensing chemical and/or biological agents from their high flying jets).
Interest in most of these other far-fetched theories remains relatively stable but the flat-Earth movement is growing, particularly in America. And it has some high-profile supporters, from basketball players to musicians, rappers to TV hosts, a number of celebrities are jumping on the flat Earth bandwagon.
So why, despite overwhelming scientific evidence, is the flat-Earth movement gaining traction in the 21st century? IMHO, it's due to a general shift towards populism and growing distrust in the views of experts, academics, scientific agencies, the government and the mainstream media. Once again IMHO, I lay this at the door of social media. A fringe group of really good "influencers" can now hold more sway than an expert in the field and very soon you can get a bunch of people around you who are constantly reaffirming your belief. These social media self-proclaimed experts are really good storytellers and people naively think, 'Oh, they're a real person, not an academic, a scientific agency, part of the government or the mainstream media so it must be true'.
The flat Earth community uses various social media platforms to create a kind of welcoming ecosystem that attracts those who distrust the "establishment". YouTube becomes a content hub, Facebook becomes an administrative one-stop shop for that hub, and then Twitter continually pushes out the message. For these fringe groups flat-earthers, et al, YouTube becomes an alternative documentary channel. Via YouTube these groups can have their daily or weekly TV show in the same way that we might watch David Attenborough, Carl Sagan, Stephen Hawking, etc.
YouTube is a powerful social media tool, more so than Facebook or Twitter because it's a "high context" platform, where users can stream themselves with an immediacy and intimacy that's lacking from text or TV specials. And unlike TV, on YouTube you can go searching for videos by people who agree with your view of the world or in this case, the Flat Earth. As we increasingly rely on social media for entertainment, we are creating an environment where misinformation easily circulates and becomes reinforced.
Look at how quickly the Flat Earthers spread the idea that the UN supported their position by their very logo which they say is actually a flat Earth map.
Lastly let me add that the results of a single public opinion survey are by no means authoritative. Differences in the phrasing of questions, variance in the methods of polling, randomness and error and (rarely but sadly) misconduct: all of these guarantees that a single survey should never be taken as the last word.