Simple, the US wanted Cuba to bow down to them, fidel said no. The US (whites) does not like any ideology that opposes there's (ask Malcom, huey, the panthers etc etc). The man who fidel replaced, Batista was put in by the US, at that time Cuba was a oligarchy, which means a few rich land owners held all the power & controlled all the resources and surprise, guess who they was in bed with? US corporations (think that 99%) (Google "banana Republic" ) I mean Jesus before fidel Cubans couldn't even visit the vacation resorts that they worked at!
Ask yourself this why are there such harsh sanctions from the most powerful country ever on a tiny island? Do you know that the US sanctions doesn't even allow other countries to trade with them. The sole reason they are poor are because of the sanctions. Cuba was /is being used as an example to any other nation who thinks of going against the grain. Most of the expatriates, the main ones anyways are family members of these oligarchs who used to be rich back in Cuba, the rest have been brain washed by the US into again forgetting that any misery being had by there people back in Cuba is 100% the fault of America