If all it takes is 3 smart motivated post-docs with no experience, then wouldn't the brain drain need to be 100% for it to be the reason?
The calculus is not simply 95% brain drain so 5% not drain so 5% will behave in this way. There is correlation between being in each group.
Or perhaps that supports your point. The smart people with fluid morality are vacuumed up by the Metas of the world, leaving none that would build a nuke for a third world dictator.