Complex sentence: After the torpedo attack, no rescue was initiated, because of the Navy's failure to track the "Indianapolis"; as she was the flagship of the 5th fleet, this failure amounted to gross mismanagement of the resource by the Navy.
Split into simpler sentences: After the torpedo attack, no rescue was initiated, because of the Navy's failure to track the Indianapolis. As she was the flagship of the 5th fleet, this failure amounted to gross mismanagement by the Navy.