Castro did actually start out doing a ton of great things for Cuba, and did his best to continue to, although with notably less success after he was caught up in the cold war proxy bull
. His biggest mistake was getting into bed with Russia - if he'd never done that, although he wasn't given a lot of options not to, he wouldn't have incurred the full weight of US economic power putting the stranglehold to his nation, and probably would've still been a hero to his people. Instead he became a cautionary tale and Cuba became a victim of cold war politics.