I don't have strong views as it's incredibly difficult to prove a negative (that it was not a leak), essentially you would have to identify and prove exactly the actual vector and even then it might be difficult to be conclusive. Lab leak seems however like a very likely scenario and it is crazy how people try to dismiss it without any actual evidence either way - and China's approach to handling the investigation and information flow definitely should cause anyone to be suspicious.
I guess at this stage thr only way we cam find out is if in 10-20 years there's a whistleblower from the lab.
1. The Wuhan institute for virology collected a naturally occurring virus then did gain of function research which subsequently resulted in infected lab workers. There's not a known virus with close enough genome sequence similarity to SARS-Cov19 for this to be plausible. It would be a monumental undertaking to induce >1k mutations in the closest known relative virus. If someone pokes around WIV or a cave in the area and finds a virus with much, much higher but not identical sequence similarity, then that's very strong evidence for gain of function research followed by a leak. In the meantime it seems unlikely that WIV would start doing gain of function research without first publishing about their newly discovered virus.
2. SARS-Cov19 in more or less its current state was naturally occurring in a location that WIV researchers sampled. The virus then escaped while WIV researchers were characterizing it. This requires one to believe that WIV workers, in a biosafety lab, were the first humans to encounter and contract and spread this virus. This is in contrast to the alternate hypothesis that unprotected workers shoveling guano, or maybe a wet market vendor got the virus. I know which possibility I would bet money on.
The point is that we don't have to prove a negative, just weigh the evidence.
The wet market was likely the first superspreader event but the patient zero (from what we know today) had no connection to it.
Also lab leaks are a type of industrial accident. Industrial accidents happen even in the places with the most stringent security protocols. Were that lab's protocols the best in the world? Can't say. And those that are best in the world have contingency plans, for when shit hits the fan.
There have been two serious epidemics of coronavirus disease in recent history: SARS and MERS. There is overwhelming evidence that both have a natural origin. Indeed, the fear of further crossover events is precisely why there was a lab studying these viruses in Wuhan.
I'm not saying that this wasn't a lab accident. What I'm saying that is that if you were actually "considering the priors" (in the statistical or strictly literal sense), you'd be concluding the exact opposite of what you're saying in this post.
This supports the idea that a jump from animals is a possible explanation. It does nothing to indicate that a lab leak is a unlikely explanation (especially with a sample size of two.)
However, the fact that this arose in one of 3 cities on the planet where this research is conducted does provide significant evidence that lab leak is a likely explanation.
Given the lack of evidence, it seems irresponsible to make strong assertions that one theory is more likely than the other.