It's because from air naval begining after WW1 and in thirties French navy strategists did not consider the aircraft at sea like an attack armament in the future but only for observation.
It's why they only converted a new class of battleships of NORMANDIE class they cancelled and kept one hull, the BEARN they completed as an aircrafts carrier for observation.
Just observe the only one carrier BEARN's aircrafts in the film didn't carry any weapons.
At war outcome 2 carriers were on shipyards to rectify this error of strategy. The JOFFRE and the PAINLEVE but too late at armistice signature coming in June 40, they were never completed.
So, French navy had several plan drawings of aircraft carriers during war but no averages to finance and materials under German occupation to build them. The country had only to wait after war to receive English and American surplus aircraft carriers: DIXMUDE(ex US freighter,ex HMS BITTER), ARROMANCHES (ex HMS COLOSSUS), LAFAYETTE (ex USS LANGLEY) and BOIS BELLEAU (ex USS BELLEAU WOOD).
It's only from 1959 that France was capable to build new thrue aircraft carriers, The CLEMENCEAU and the FOCH.