Every other theory requires involving many more unsupported hypotheses.
This would be obvious to the majority of the HN population in most cases, but the disinformation in this case is apparently quite effective.
It doesn't make much sense to single it out here, the most plausible version of the lab leak hypothesis is that covid is the result of cooperative research undertaken by American and Chinese scientists and funded by both governments
Edit: I'd love to receive a substantive counterargument from the downvoters
As for the Americans, their culpability in helping make the lab I think would be seen as a small thing.
Paradoxically, it may be in everyone's interest for the plebes to never find out the truth. If there was magically some 'hard evidence' to appear, right now, that made China culpable ... we would be heading into another, massive recession. There would be riots around the world, Asians in every continent would face threats of violence and attacks for a decade. Forget America where those things are talked about ... you can forget being Chinese in Poland, it would be painful.
The populism would be intense and ferocious, but not only that, regular institutions, businesses, CEOs etc would also be upset for very good reason. I can see China facing lawsuits for literally Trillions of dollars.
It could feasibly lead to a chain of events sparking a war.
This is completely conspiratorial, but I honestly wonder if the West actively doesn't want to push for the truth because it would do more damage than good. If China knows 'they did it' they're probably going to make the changes necessary so it doesn't happen again, for their own benefit, and it's unlikely they need international pressure or the threat of litigation to improve those pressures. But that's just a fantastical idea.
Basically 'The Truth' is a different thing than 'The Impact of Public Information' and both of those things matter. It's a scary thought but it's the Realpolitik of information.