I thunk to understand what went wrong here you have to consider a kind of feedback loop between our media and the CDC/WHO scientific establishment.

If Covid-19 had been some kind of Ebola-type virus I think things would have been different because the results would have been too obvious to ignore. If it had started in Sweden, then we wouldn't have had to worry about xenophobia or encouraging the more virulent infection: racism. But covid fell into a difficult middle ground where motivated reasoning went strongly in one direction and where the relevant evidence wasn't too strong to rationalize away.

As usual, I blame the media. They're the primary enforcers of orthodoxy. At the most extreme they can get a scientist fired for saying the wrong thing. But they also establish the right kind of thinking (not being xenophobic or racist) vs the wrong (things that would lead to travel bans).

Masks imply a scary disease and it's important that the public thinks everything is under control so they don't get all xenophobic, and because we can't absolutely say they are proven to work we'll say they don't. That seemed to have been the reasoning.

What we really needed was people willing to be thought xenophobic.

The media of course loves science: under these conditions. Matthew Yglesias of Vox just wrote a piece about how angry he is that the media was misled by the experts on the mask issue. They thought they were being responsible and following the experts. But really I think Vox et al are the ones who create this environment. I'm pretty sure something similar was going on in China between their scientists and the CPP, but a bit less subtly in that case.