[dennis_jeeves2]

>That when you drain the most smart/productive people away from every other country, all those countries become less wealthy and more dysfunctional, leading to societal decline, poverty, resentment, radicalisation, war, etc?

Societal decline, poverty, resentment etc.: why should functional people bear the burden of it? Brain drain happens for reasons beyond the simple need to earn more money, it also happens because dealing with those dysfunctional people is extremely draining at several levels. On a larger scale when putting smart people together - be it at a country level or even at a company level, one achieves things that are not normally not possible, which is a net benefit for the world at large even if it creates some populations that are dysfunctional.