Basically, Reagan and his economic plans made it possible for companies to flourish and also this meant that the economy was developing and people had money. Opposite to this, the Soviets were starving because of things like high corruption and heavy regulation. Many countries that were part of the Soviet Union wanted to separate and become independent and adopt the Capitalism system as seen in the US. The Soviets responded by opening up a bit but it was insufficient. Immigration was heavy because there were a lot of people who went there willing to work because their countries of origin were poor. It's different because immigration is nowadays mostly not from Europe like it was at that time.
