Do you have more specifics on what the critics were ? I have the intuition that you can't really do good science in a totalitarian regime (because superior pressure is too high, and totalitarian regimes are often associated with "fear to fail" state of mind), but it's just a belief.
They think a lot of the science is just made up and not rigorously tested at all. They also dislike the way promotion and advancement is done there, not based on the scientist's merit but based on who you know, nepotism, corruption, etc.
I don't doubt it but don't you think it would be easy to find American scientists that feel the same way? Also I'll just point out that your sample is biased to people who have chosen to leave. Of course they made the right decision!
