In addition to the interest in casinos, wasn't Cuba also a major route for getting heroin into the country?
I seem to remember something about after WWII Lucky Luciano facilitating heroin routes from Sicily to the US and Cuba was mentioned as one of the portals... I may be wrong.
http://www.drugtext.org/library/books/McCoy/book/09.htmPost Edit - I found this link. Of course, I can't vouch for accuracy but it is at the least pretty interesting.