Something I think is plausible is that they've figures out a technique for controlling the narrative in the internet age where they take the range of opinions in a group with positions they don't like, identify a really wild one, debunk it, then tar the whole group with that opinion. I'm not thinking any particular group, although I'm guessing it is deployed against literally all political protests. The technique really needs a well known name.
I doubt that is happening for lab-leak stuff since nobody is making money off it (and if the Chinese government cares they can just restrict access to info). But it is really interesting to note how difficult it was to restart the conversation once the lab leak theory was "debunked", so I'm sure the technical people who want to control the narrative took note. It was a nice clear example of how the dynamics come together.