A well written letter
What else can be expected, when the responsibility for oversight of the regulatory compliance of a "For profit" private sector enterprise is divested from a public sector agency with little or no interest in the profitability of a private enterprise, and turned over to a "For profit" agency. Who in turn is, in part, dependent on the profitability of the private sector enterprise to insure the agency's own profitability.
This basically leaves little or no incentive for the private sector enterprise to correct defects because they know there is little or no chance they will be held responsible, even when they are ultimately responsible for scheduling and providing funds for preventive and corrective maintenance. They also know that if the regulatory agency were to go after the ship owner/manager the "For Profit" regulatory agency would be "Biting the hand that feeds them". It is also still too easy for management through various means such as various forms of intimidation or after frustrating the seafarer by ignoring even their documented complaints, to make like the the Seafarer is responsible for his or her own misfortune. Seafarers, especially high priced ones, are expendable in favor of less expensive seafarers who will accept defects will not "Rock the Boat"
It is also well known that there are, for every high profile case like this one, dozens of other ships around the world that disappear in the same mysterious circumstances that do not even get a parting mention.
After all It's "All about the Money" and "Dead men can tell no Tales"
Troubleshooting 101 "Don't over think it - K.I.S.S. it"