From your article: "HSBC did so, they say, by not adequately reviewing hundreds of billions of dollars in transactions for any that might have links to drug trafficking, terrorist financing and other criminal activity."
From the indictment: "Shrem email accounts reflect that 'BTCKing' not only obtained his supply of Bitcoins through the Company, but did so with extensive support from SHREM."
If the DOJ had an e-mail trail of anyone important at HSBC giving personal technical support to a drug cartel, the outcome would have been very different. Remember, "allegations" are just that, and there is a gap between what the prosecutors might allege and what they can prove in court. The proof in this case is a slam dunk. It combines explicit support for BTCKing with explicit knowledge of his illegal activity. In HSBC's case, that link is missing. You have emails like the one you quoted, which could be interpreted as wrongdoing, or could just be interpreted as figuring out how to let a client do what he wants in a legal way by dealing with a different office.