SARS-CoV-2 has relatively low IFR, especially among younger people, and a mild case is easily dismissed as a flu or cold. Transmission is also heterogeneous, with most patients infecting no one while a few infect huge clusters; R = 2 absolutely does not mean one patient infects two, who infect four, who infect eight, etc.

> An important feature in this distribution, consistent with earlier findings (4), is that the majority (76%) of infected cases shows no evidence of onward transmission amongst any of their contacts.

https://pmc.ncbi.nlm.nih.gov/articles/PMC7523148/

So there's no reason to expect that the first cluster that generates enough sickness and death to attract official attention will occur near the point of introduction. If we look at North America, then it in fact did not--the introduction must have been at an airport or seaport, but the first large clusters were in nursing homes, church choir practices, etc. This is different from SARS-1 or MERS, which were deadly enough to make that cryptic spread much less likely.