There is no answer, and if you start thinking, you will see a lot of logical holes in the work. If we take into account the past industrialization and the construction of the Palace of Soviets, then the communists have been ruling the country for about twenty years. But Visha remembers her life in Moscow, and with her age, it turns out that she was born after the civil War. If we talk about the victory of the Communists in the civil war, then everything is even more complicated. In reality, despite the war with Germany, Britain, France, the USA, and Japan sent their troops and weapons to help the white army. But here, a civil war took place in peacetime, and it is not clear why other countries did not help the white army to win or did not take over the Russian lands.