What you are missing though, is that up until now, Taiwan never had enough cases (and does / did have very tight monitoring) to where virion levels, say, in a bunch of those trains, would get away from them. Sure, a few outbreaks occurred, but, they caught them and squelched them.
I suspect that in the case of moderately high infectivity and moderate population mobility, high population density may actually make tracking & containment easier.
Omicron may of course blow that up.
HERE, obviously we never had a chance at containment.
One thing is interesting though. At least prior to Omicron, high population density even in countries with poor tracking (etc.) has not been a consistently noteworthy COVID accelerant. Hmmm......
Someone at CDC has to be assigned to this. Surprised there has been no report.
They were right next door to the CCP so they knew what was up in China when the Wuhan flu was going on. Plus it was easy for Taiwan to control their borders and they were able to shut down their international flights really quick.
President Trump did shut down all flights from China. But that was too late. And it didn't matter if flights were still coming in elsewhere (especially Europe where they were still flying in from China).