Your logic here isn’t sound. “Why not 5 years ago?” - the mechanism here is that each year there is a low but non-zero probability of a virus jumping to humans.

Your logic here isn’t sound. “Why not 5 years ago?” - the mechanism here is that each year there is a low but non-zero probability of a virus jumping to humans. That is why you have infrequent intermittent epidemics like Spanish Flu, or more recently SARS, and not constant evolution of new crossover viruses. It seems that crossovers happen more on the timescale of decades than mere years. (Though I’m excluding crossovers of unviable infections that don’t go anywhere, of course). None of the above argues against the lab escape theory. As the OP details it’s possible. Just your specific line of reasoning here oversimplifies, hence the downvotes.