They went on strike to try to get better working conditions and better pay. They would organize company wide strikes and protests. The government at first ignored this because at the time the US believed in social darwinism. Later, eventually, the US government will implement labor laws.
Answer:
Historians collect and evaluate information from many primary sources to answer questions about historical events, a process known as the historical method. They may analyze written records, physical artifacts, and other types of evidence during the course of their investigations.
A very contributing factor was the Bay of Pigs Invasion in 1961, when the US(CIA) tried to execute a military invasion of Cuba. Cuba likely felt threatened by the US, and invited Russia to boost its internal protections.