Why Norfolk's destroyer-leader label did not require heavier guns

Why did Norfolk have only three-inch guns and antisubmarine armament despite being a destroyer leader?

The three-inch armament was considered a better fit for its intended duties and missions.

Norfolk's three-inch guns and antisubmarine armament prompt a question about whether it was lightly armed for a destroyer leader. The explanation rests on the duties expected of the ship. Three-inch guns were considered more appropriate to those duties.