Cuba has pardoned 787 prisoners in response to a call by Pope Francis to consider granting inmates amnesty. Those pardoned include female, young and sick prisoners but not those who have committed "extremely dangerous" crimes such as murder or rape. Pope Francis played a key role in the rapprochement between the US and Cuba, and the Pope received a warm welcome last year on the island.
Cubans are predominantly Catholic, despite the fact that thier country has been communist for many years. Cubans have great respect for the pope as a result, and anything he says will have a major effect on them. If not the biggest reason why the pardons were made, his words are a contributing factor.
It does not make sense for one pope to affect Cuban actions when all of the other popes, since the Cuban communist revolution, failed to do so. The Catholic Church has long had a policy of mercy and peace. Since the Castros have been in power all this time, it's doubtful.
Pope Francis is not as influential as he thinks he is. Ultimately, politicians do what they are going to do. The Pope is more responsible for setting a tone around the world. He does not do that much to influence politics. There are different spheres for politics and religion, and the Pope is more of a social figurehead than anything.