If we recall, initially China downplayed how widespread the virus was and made it out as if it were contained. Perhaps they did not know how widespread the issue was either. Further, at that time there was complete uncertainty regarding Covid-19's virulence (it was after all, a completely brand new virus; and there was a ton of uncertainty around in January 2020).
Regarding to the communication from the US government of how contained the issue was, as a reference, the president at the time wrote:
"Jan. 24, Twitter:
“China has been working very hard to contain the Coronavirus. The United States greatly appreciates their efforts and transparency. It will all work out well. In particular, on behalf of the American People, I want to thank President Xi!”"
- https://www.politico.com/news/2020/04/15/trump-china-coronav...
Basically, the entire world needed to start quarantine in early January of 2020 to effectively nip this in the bud (shutting down international travel, regional travel, etc). Perhaps that needed to have even started in December. I would suggest then that Beijing didn't shut down international travel at that time for the same reasons that the rest of the international community did not. In part they were still downplaying it as was the public oration from the US government was downplaying it as well. It wasn't until late February and into March that it became well known publicly that this was a new pandemic.
Hence, by March China was fully shut down, and at that point there is no hiding the issue (why is all of China locked down?), and at that time it was everyone's problem.
> A) Poor information propagation
There was some info released that the CIA assessed the virulence opportunity to easily be a pandemic as early as November 2019. That poor information propagation wasn't necessarily just a problem with the Chinese government.
Citation: "Intelligence report warned of coronavirus crisis as early as November: Sources" - https://abcnews.go.com/Politics/intelligence-report-warned-c...
The clamp down on information exchange does not strike me as the actions of a group with everyone else's best interests in mind. And given that we have hitherto been pretty chill with China on the whole, I really think if they had gone "screw it, international travel lockdown"; you'd have seen materials and humanitarian relief being flown in in order to help out with citizens stranded overseas. We may not even be having this conversation, because to be frank, how China did decide to react just doesn't make any sense except in the context of someone with something to hide.
There's a hanful of ways you can look at that:
Wuhan International couldn't be closed without consent from Beijing.
Beijing didn't grant it because
A) Poor information propagation Or B) Someone made a weighty geopolitical decision that in order to best serve China's interests, it was time to make this everyone's problem, leaving the International Airport open as a result. Or C) some combo of the two.
I don't know your particular balance in regards to the actual Overton Window as extended to humanity as a whole, but I damn well know where it registers on mine.