60 tons may seem like a lot, however it has to be put in context of the boat's total weight/displacement. Bayesian's displacement was 534 tons, thus the ballast represents only about 11% of the boat's total displacement. By comparison my Sabre 362 has 5,520 lbs of ballast and a designed displacement of 13,800, the ballast is 40% of the boat's total displacement.
Hull stability is a function of more than just ballast weight, it also includes where the weight is located, where the center of gravity is located, the shape of the hull, and more.
In a year or so there will be a final report by the Italian Coast Guard on the cause of the sinking. We're just going to have to wait while the investigation is conducted and be wary of the armchair Naval Architects and their opinions.