The internet and social media have enabled vast numbers of easy-to-spread memes to be created and subsequently enter competition with one another. The outcome of this universal Darwinian struggle for attention will be memes that are optimized for propagation. Truth will tend to spread less effectively than fabrications under certain conditions. For instance, many incorrect or insane beliefs don't have immediate concrete penalties for those holding them, especially when people can avoid public ridicule by insulating themselves in like-minded echo-chambers. Without the mechanism of falsification, there is no feedback that can encourage a correction in such beliefs.
Furthermore, the growing influence of secularism at the expense of religious affiliation has left a "God-shaped hole" in people that must be filled with some other system of belief (indeed, the specific capacity for religious belief may have been an evolutionary adaptation in humans by establishing a meaning to existence and fostering the emergence and enforcement of pro-social moral norms). This subconscious fervor in seeking unfalsifiable religious-like systems of belief may help further entrench such views. If trends continue, society's ability for sense-making will continue its post-modernist decline and lead to an acute existential crisis when a meaningful share of people have become mentally incapacitated by ideological anti-rational mind-viruses.
This sounds good on the surface, but I'm not buying it since plenty of people with God-filled holes tend to believe this crap.
People have always responded to conspiracy theories. The difference now is that conspiracists have better access to people than they ever have before, and therefore there is a much bigger machine investing in perpetuating them.
Also, globally religion isn't in decline, the percentage of the population that defines itself as religiously unaffiliated is actually shrinking.
I don't think we (yet) have the same sort of problem globally as in the West, and in particular, in the US. The West is where the most
Extremely Online people can be found exposing themselves to various ideologies that have been weaponized through Darwinian selection. To a growing extent, the rest of the world is not far behind--perhaps a decade. And while it may be true that religious affiliation is increasing globally, it is
decreasing in the US. Conducting a study on the relationship between religion and other ideologies would require some careful work to disentangle the causal factors at play. Discarding this hypothesis leaves the rest of my point intact, however.
I completely agree with your point that the potential for incorrect ideas has always existed and what has changed is the scale at which such spread can occur (was it Stalin who said:
Quantity has a quality all its own?). Prior to social media, those pockets of insanity would be--usually--self-limiting in their scope (a notable exception being the major religions which have co-evolved with our institutions for 50-100 generations). The advent of newspapers and mass media started the process allowing a much faster uncontrolled spread of ideas. And today, perhaps a tipping point has been reached where the ease and speed at which ideas can spread can overwhelm our native ability to perform error correction at an individual or societal level. A nuclear bomb is just a warm lump of metal until compressed beyond the critical mass.
