Main cause communism. The north did not want to adopt communism while the south did hence the reason for why the US got involved to make sure that the north would win so as to help stop the spread of communism (sorry i know this is kind of late)
At first they believed that Cubans were building factories for airplanes and ground to air missiles that would be used to attack US airfighters. However, they soon realized that the weapons made and delivered were actually nuclear missiles and they decided not to allow them to reach Cuba
The new deal goes down in history as fixing the problems which historians refer to as the “Three R’s” so essentially the New Deal fixes these three problems:
Relief for unemployed and the poor
Recovery of the economy to previous levels
Reformation of the financial system to prevent another depression from ever happening again.