Was it truly ideological? Was Cuba trying to establish itself as some kind of world power in its own right? Was it some material interest? I guess the question also applies to Cuba's activities in the Congo.
Hi there. I wrote an answer to a similar question a little while ago that you might enjoy taking a look at. True ideological/internationalist explanations are popular in the current literature, as opposed to a 'power grab' or Soviet direction. Hope its useful!