Cuba became a socialist country in the 1950s under a revolution led by charismatic speech-maker Fidel Castro. The revolution was largely a reaction against the monopolistic practices of many US companies in Cuba at the time.

Predictably, the Cuban economy is stuck in the usual socialist time-warp, and they haven't moved on since the revolution.

They were getting massive subsidies from the Soviet Union during the cold war, but it was a two horse race and they backed the wrong one. Even now the US will not trade with them.

Leftists like to blame Cuban poverty on the US sanctions. They apparently have no trouble reconciling their belief that free trade (ie globalization) has destroyed other economies, but lack of globalization has destroyed Cuba's.

Historically, the only international policy the US is capable to pursing to a proper conclusion has been the bankrupting of communism. The US will trade with Cuba when Castro is dead, then their economy will develop. Castro, facing the reality of being just another dead dictator, is trying to enshrine socialism into the Cuban constitution. This will only delay the inevitable.