While the rum running helped, I think most of the Kennedy fortune derives from stock market fraud and manipulation the elder Kennedy engaged in during his stint as a banker. He traded on insider information, and formed syndicates where members would buy and sell stock among themselves. Once the public saw the “good performing” stocks, they would buy in as the Kennedy crew would sell, as the stocks would crater. It was this fraudster genius FDR was looking for when he selected old Joe to be the first chairman of the SEC. Once appointed, Joe made illegal, all the tricks that enriched him and friends.
BINGO !