Matt Yglesias has a long essay laying out the timeline of the theory that Covid-19 escaped from a lab in Wuhan, and especially the media coverage of that theory. (If that link won't work, try accessing from Marginal Revolution). Despite what you could have read in the Times and many other places, there was never a scientific consensus that the virus emerged from the Wuhan wet market. The very first serious western publication about the pandemic's origins, in The Lancet in January 2020, pointed out that several of the first cases had no connection to the market, including the earliest case so far identified.
Then Senator Tom Cotton, a noted China Hawk, started saying the virus might have escaped from the Wuhan virus lab and demanding more information. For this he was attacked across many media outlets on the left and the right – remember that at that point Trump was downplaying the virus and saying the Chinese had it under control. The fact checkers at Politico 1) said Cotton had claimed the virus was a Chinese bioweapon, and 2) gave him a "pants on fire" rating for that claim, which he never made.
And so it went. Many media outlets said it was the "scientific consensus" that the virus came from the market, which it never was, and many equated the claim that it escaped from the lab with the claim that it was an engineered bioweapon, when those are totally different things. Scientists who tried to argue that the market theory was implausible were shouted down on Twitter and called "conspiracy theorists" in the press.
What especially interests Yglesias is the manufacturing of a "scientific consensus" where there was none:
Beyond the gross irresponsibility of the earliest media coverage, I think the story of Dr. Chan and her struggle to be heard illustrates the perils of expert dialogue on social media.
Social media is truly social in the sense that it features incredible pressures to form in-groups and out-groups and then to conform to your in-group. Unless you like and admire Cotton and Pompeo and want to be known to the world as a follower of Cotton-Pompeo Thought, it is not very compelling to speak up in favor of a minority viewpoint among scientists. Why spend your day in nasty fights on Twitter when you could be doing science? Then if you secure your impression of what “the scientists” think about something from scanning Twitter, you will perceive a consensus that is not really there. If something is a 70-30 issue but the 30 are keeping their heads down, it can look like a 98-2 issue.
I do not know a lot about science, so I will not opine how generally true this may or may not be.
But in economics, which I do know well, I think it’s a big issue. If someone tweets something you agree with, it is easy to bless it with an RT or a little heart. To take issue with it is to start a fight. And conversely, it’s much more pleasant to do a tweet that is greeted with lots of RTs and little hearts rather than one that starts fights. So I know from talking to econ PhD-havers that almost everyone is disproportionately avoiding statements they believe to be locally unpopular in their community. There is just more disagreement and dissension than you would know unless you took the time to reach out to people and speak to them in a more relaxed way.
My strong suspicion is that this is true across domains of expertise, and is creating a lot of bubbles of fake consensus that can become very misleading. And I don’t have a solution.