Why communism under Fidel Castro succeeded in taking Cuba?
Initially, the US seriously underestimated Castro. Cuba, like many other Latin American countries had a long history of political instability and insurrection. The US initially believed that Castro was just another in the long line of Latin American strongmen who would come to power promising reforms, and who eventually would be bought off by American money (as was the case with so many others before him). What the Americans didn’t count on was the influence of the Soviet Union. Castro had been a communist during his days in Mexico, and when his forces took control, the Soviet Union backed him financially and militarily. The Americans were totally unprepared for this, as, since the days of the Monroe Doctrine, the US was used to having its own way in the Western Hemisphere. They underestimated Castro’s committment to Communism, and didn’t anticipate the forthcoming aid from the Soviet Union, without which, Castro could never have consolidated his power.