People who actually develop tanks usually have restriction for going abroad for 5 or more years even after they leave they job because they know classified information. So I don't think that they left the country.
Perhaps for those who start the job. But if you're a Moscow State University engineering graduate, why would you even start when there are better available living situations? Sure maybe some stick around for familial/patriotic reasons, but most are going to leave for greener pastures.
