Complex sentence: The attempt failed, in part because Admiral d'Estaing did not land French troops prior to sailing out of Narragansett Bay to meet the British fleet, and then sailed for Boston after his fleet was damaged in a storm.
Split into simpler sentences: The attempt failed, in part because Admiral d'Estaing did not land French troops prior to sailing out of Narragansett Bay to meet the British fleet. He then sailed for Boston after his fleet was damaged in a storm.