When Stalin took over the USSR in 1929 it was dirt poor, 95% of the population were peasants, the USSR was pushed around by smaller countries and was weak and poor
When he died in 1953, the USSR was the joint first most powerful country in the world, had almost single handily defeated Nazi Germany, and was in control of all of Eastern Europe, including Poland
The leader of the USSR from 1953-1964, outgoing and a lot more relaxed than Stalin, was determined to make the USSR a better place to live, closed the gulags (prison camps in the USSR)