Adm Harr was relieved because our Allies thought him too old and lacking in fighting spirit. Which was ironic, because history shows him to be the most competent of the high ranking allied officers In the area. The only naval victory the ABDA fleet won in the first months of the war was under Hart.
Also he had health problems caused by the need for extensive Dental work. Admiral King was very sympathetic toward Hart and allowed him to keep his rank of full Admiral. Roosevelt met with him and realized Hart knew exactly what he was talking about in how to handle the Japanese. It is terrible sad he was not unitized more in the Pacific War effort. he went upon to become a U.S. Senator from CT.