Forums, email chains, IRC, Usenet, etc. there's several things that make it more potent and spread faster now. For starters the internet is less balkanized, so

Forums, email chains, IRC, Usenet, etc. there's several things that make it more potent and spread faster now. For starters the internet is less balkanized, social media platforms are magnitudes larger than the largest forums ever were so an idea can just spread faster and further than before. Email chains could approximate the reach but other factors meant they were less potent and also I think people had fewer emails known in their address books than they generally have friends on social media though I don't have any numbers to back up that gut feeling. Although things are just randomly shared outside of social nets by social media algorithms so that would also help it jump outside of limited social groups too. Next the medium is just inherently more engaging now that photo and video are first class citizens on the major platforms, they're way more attention grabbing and engaging than a wall of text could hope to be. Also I think fundamentally there's an imbalance between how easy it is to lie and to debunk a lie and how much each of those will spread. A lie is exciting/angering and people will spread it much faster than the 800 word debunk that explains just how full of crap the lie was (and often how the person spreading it is using it as a trojan horse for other shittier ideas). "Everything you know about X is wrong" spreads faster than "No most of what you knew was basically right and here's the history of X," it's shocking and new vs familiar and old. Finally I think there's a fair amount of blame on the structure of *feeds and the algorithms that place things on them. It optimizes for salacious, shocking content that gets people to share it because that's what the algorithm selects for (roughly), things that keep users on the site so more ad impressions can be served. Add to that bad actors willing to lie and twist the truth to make money and a decade or so of Darwinian corporate evolution and you've got a pretty nasty combo.