Why did the French remove themselves from their religion?

Answer 1

The French suffered severe religious troubles in their history.
- religious wars between Catholics and Protestants. The Catholic church gained the upper hand in these conflicts. The bad memories from these wars lasted for centuries in French society.
- Troubles during the French Revolution, during which an antireligious sentiment led to the outlawing of priests, opposition by the church to the principles of Revolution, etc... The situation eventually settled down as moderates came back in power. A result was the appearance of civil marriage, or civil servants keeping birth registries instead of the parish priests.
- At the end of the 19th century a forceful antireligious movement (especially anti Catholic, since the Catholic church was the only sizeable religion) reappeared. It ended with laws of strict separation between church and state, passed in 1905. It was forbidden to establish cemeteries in church yards, for instance.
From then the French constitution established the neutrality of the state (versus the precedent situation where France was constitutionnally Catholic) and secularism became entrenched in French life. A mainstream opinion is that anything fiercely religious (proselytism in the first place) is suspicious and contrary to French culture.