Glenn Kessler has a piece titled Timeline: How the Wuhan lab-leak theory suddenly became credible:
How and why did this happen? For one, efforts to discover a natural source of the virus have failed. Second, early efforts to spotlight a lab leak often got mixed up with speculation that the virus was deliberately created as a bioweapon. That made it easier for many scientists to dismiss the lab scenario as tin-hat nonsense. But a lack of transparency by China and renewed attention to the activities of the Wuhan lab have led some scientists to say they were too quick to discount a possible link at first.
It did not “suddenly become credible.” It has always been credible. Jim Geraghty had the evidence back in April 2020. The problem is that the “fact checkers” of the world missed it because they were hellbent on mocking the bioweapon theory, and refused to see the difference between that and the more plausible leak theory. Caleb Howe had a joyous post last month about how Big Media mocked the idea. It’s still worth a read.