Oli and TB both good points, but I think the real problem with Sonny's being hot to get into the drug trade was his inability to think long term. He saw " a lot of money in that white powder," but he did not think through the consequences. Vito had to good sense to realize he would lose political and judicial support if he went into drugs the same way he went into women, gambling and labor unions, but Sonny did not. Of course what no one foresaw was the vacuum the drug trade created within the Sicilian mob and the takeover of the trade by Colombians and later Mexicans.