Alina Chan of the Broad Institute (MIT, Harvard) doesn't think it is likely that Covid is the result of a lab escape. However, as she thinks it is possible, and when she discoverd some evidence that its structure is not fully consonant with an animal-to-human jump for the virus, she got a lot of attention fast, both positive and negative. The linked article can give you a summary. The short take is that with a novel virus, mutations that improve transmissability are usually the first things one sees, as even small increases in ability to spread are advantageous for the virus. But the early samples of SARS-2 seem to be a little further up the line. Curious.
Her first point is that the division into either-or answers misses a lot. To merely raise the question of origins, even when most of the scientific energy has gone into finding a vaccine or cure, has had people accuse her of being a conspiracy theorist. On the other hand, irresponsible reporters from the skeptic side have put forth her statements as showing that there is great evidence that the disease was a Chinese lab error, or even a bioweapon. She points out there is a continuum. If the lab was sending lots of researchers out to bat caves, food markets, and remote farms to collect samples and expose themselves to possible mutations, then that would be an entirely natural development of the virus - but it's spread might be largely due to the lab's involvement. Similarly, if they were looking at a sample, focusing on a particular site and tweaking something, just to see what it changes in terms of the organism's behavior, you might accidentally but not maliciously make it slightly more transmissable or more dangerous. That is, it already had the ability to infect humans, but you just made that a little more likely. A further possibility is mixing and matching genes between different viruses. I guess that isn't considered all that odd now. Scares the bejeesus out of me, but maybe it's a mostly safe intervention.
On any of these, it would suggest that the virus existed in some less-harmful form earlier than the currently discovered version. Think of it as a pre-covid or proto-covid. That would at least be a plausible explanations why this odd data of Covid existing "too early" that occasionally shows up might be so.
You can see why lots of people would have interest. Even if it was unintentional, all the research was being done responsibly, and this was just an unfortunate accident, the PRC would not want this to be known. Also, if this is a common technique and considered necessary even by researchers unrelated to anything Chinese, they might be unwilling to have this be generally known, because it would invite regulation by governments, which they know in advance is likely to be stupid. The interview with Chan I listened to was from January, and she and the interviewer both agreed that the possible lab origin theory is not being slammed down without a hearing quite so much anymore, and thought it possible that because the idea might have helped Trump, now that the election is over many scientists might be less-opposed to the investigation. That's ugly, and unprovable, but fits my prejudices pretty well.
Chan has also had colleagues tell her to her face that she is just attention-seeking. That seems unprofessional. I thought she was pretty convincing she has not liked the attention she has gotten from this, from many sides, and has wondered how life would have been different if she had never gone on this project. She is originally Canadian, brought up in Singapore, and is pleasant but I don't think she scares easily. Her stated goal is to learn of the origins because she is curious, and we need to know about origins if we are entering a pandemic world where one of these shows up every five to ten years.
If there is only a 5% chance it's true, it's worth looking into, right to the bottom.