Lexington's thin armor is better explained by the intended enemy and mission than by a simple failure to understand British battle damage. The ship was built for a Pacific war against Japan, finding the Japanese fleet and allowing the American battle line to choose its engagement. American lessons from Tsushima emphasized the danger of letting Japan dictate the time and place of battle, so scouting speed took priority even though the design remained dangerously vulnerable.
Notable Point · 22:35-25:11
Lexington's thin armor followed a Pacific scouting doctrine
The armor scheme becomes more intelligible when Lexington is treated as the fleet's fast finder rather than a ship intended to fight British capital ships.