My understanding is that this is what gain of function research is all about. Accelerated evolution within a lab towards infecting a specific species.
It doesn't have to be crispr introducing reach mutation.
It doesn't have to be crispr introducing reach mutation.
You don't get there by splicing an ACE2 spike onto an RaTG13 backbone and passing it through a dozen mice. That gives you something that still looks similar to RaTG13 and infects mice.
The ACE2 spike also looks most similar to a previously unknown ACE2-binding spike protein found in malaysian pangolins.
So WIV would have had to have discovered that pangolin spike-protein, kept it secret, spliced it into an RaTG13 backbone, then not used mice but passed it through a species like that had a human-like ACE2 for a decade and millions of animals.
An alternative hypothesis is that Charles Darwin did that experiment.