Best guess is that it started after WWII; it basically ignores France's illustrious military history prior to 1940, including Napoleon and the Victory in WWI, and portrays the collapse of France in 1940 as symbolic of the French 'national character'.

It's also worth noting that this subsequently ignores the French Resistance and the Free French Forces, and the actual REASONS why France was ultimately unable to defeat the German armies in 1940 (and not for a lack of trying I might add!)