Why did rochambeau favor engaging the british in chesapeake bay?

When the Rochambeau's expeditionary forces arrived in July 1780 at Newport, Rhode Island, George Washington had already ordered American forces to be transferred to his encampment near West Point, New York, to support an attack against New York City. Rochambeau insisted that an attack on New York City was not feasible and that the French had promised their naval support only on condition that the main objective would be the capture of the British forces in Chesapeake Bay, Virginia, where General Charles, Lord Cornwallis, was establishing a major base.