Communist revolutions have been attempted across the world - what were the primary reasons that the Cuban Revolution succeeded while others failed?
The Cuban revolution succeeded because it was a broad-based revolutionary movement, not a "Communist" revolution (initially, that is). For instance, in the July 26th (1953) uprising against the government's military barracks (the equivalent of John Brown's raid on Harper's Ferry before the U.S. civil war), the Castroites were only one of several revolutionary groups revolting against the unpopular dictator, Batista.
Castro was captured and condemned to 15 years' imprisonment, but was released in 1955 under a general amnesty.
In 1956, the Castroites fled to Mexico, where they were joined by other revolutionaries, notably a student group called the Revolutionary Directorate (RD). This group returned tin Cuba in 1957, and launched a suicidal attack against Batista, while Castro bided his time and returned later.
By this time, Batista was losing most of his supporters. In 1958, the U.S. recalled its Ambassador and withdrew its diplomatic recognition of Batista, placing a key embargo on military goods. Meanwhile, one of Batista's opponents was an American "soldier of fortune, William Alexander Morgan. When Castro returned, he was joined by Morgan and the surviving RD members. Their combined efforts were enough to bring down Batista.
After the Revolution was successful, Castro's Communists "hijacked" it because they were better armed and organized than the other revolutionaries. But that is another story.