But for the Washington Naval Treaty, the 8 inch gun would have been quickly eclipsed

Frank Fox has told me that plans were afoot, by 1921, for large light cruisers to be armed with calibers greater than 8 inches. The 10,000 ton number and the 8in gun were due to the existence of the Raleigh class cruisers with 9-7.5in guns and a displacement of 9,750 tons standard. This was a time when the beancounters of the world prevailed and stopped the building programs which were underway at the time. The Washington Naval Treaty was one of the high points (or low points) of the Harding administration. The sentiment matched the inclination of cost-cutting politicians in Britain and other countries, as well. Japan was forced to comply, as they would have perferred to keep building.