The most likely origin of this virus at this point, was an accidental lab leak due to a quirk in regulations where BSL 2 was the category approved for normal coronaviruses, and BSL 3 was reserved for the natural strains that already infected humans like SARS 1 and MERS.

Unfortunately nobody in the lab bothered to question whether they should be using BSL 3 gear when they were breeding bat born Corona viruses with humanized mice.

That's the most likely explanation: This doesn't happen too frequently because normally somebody has the brains to ask themselves if the virus they are creating requires a greater level of protective gear than what the rules call for.

For anyone that questions this comment and thinks that I'm some lunatic pushing conspiracy theories feel free to look at the NIH grant that funded this research and noticed the specific phrase of humanized mice.

https://reporter.nih.gov/search/xQW6UJmWfUuOV01ntGvLwQ/proje...

Bear in mind that in the early 2000s it only took 4 months to find the intermediate host between bats and humans. For mers it took 9 months to identify camels as the intermediate host.

Despite having orders of magnitude more funding nobody has found an intermediate animal host for covid-19. Common sense tells you there was an intermediate host and it was the humanized mice in the laboratory.