disclaimer - I really dont know the answer, but ive got some impressions which are just impressions, might be bullshit
but maybe its
-france has yet to experience the legal crushing of its trade unions a la thatcher, so trade unions more effective, and virtuous circle so have more support
-a stronger organised left. theres a communist party festival that attracts nearly a million people in france
Fête de l'Humanité - Wikipedia
-a less subservient relationship to the state. vive la republique attitude must be some kind of factor, cementing the role of people power in peoples minds
-these things have momentum and france hasnt lost it.