The MSM has never mentioned it, but a few weeks back I was listening to a podcasts with virologists and one of them mentioned that coronaviruses have the special ability to combine themselves with other coronaviruses to exchange genetic material (called
homologous recombination, similar in function to sexual reproduction), in the process creating a new coronavirus. The current hypothesis is that the pangolin coronavirus (which uses a human-compatible ACE2 receptor) recombined with another bat coronavirus inside a host, creating this virus.
Here's a paper on it, but there are lots more. So as it stands this would be the Occam's razor explanation, and not the laboratory mess up explanation that I thought might be possible in the beginning.
It's also possible that our current SarsCov-2 virus could go back into animal reservoirs, for example bats, and recombine with wild coronaviruses to create a new virus we wouldn't have immunity for at all. This underlines the importance of humans reducing contact with animals that are able to be infected by covid as a much as possible, you don't want them to be infected and the virus to go back into the wild. On the macro scale, we want vaccines and herd immunity as quickly as possible to reduce chances that an infected human comes in contact with an animal.