The initial cluster was found at Wuhan, because there's a lab there. We have no idea how many sub-pandemic clusters arose and fell before this particular mutation got into a population sufficiently dense and mobile to spread it.
Did you know that 1918 flu arose in Haskell County, Kansas, killed many, and then just .. died out? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC340389/