I’m by no means an expoert in French ecclesiastic history, but I know that the relationship between the French government and church has a long history of struggle.
In the 1789 revolution (or maybe later, during the Terror), the church was abolished, church lands confiscated, and priests punished, in favour of the new quasi-religion of Reason. The catholic church still had quite a lot of popular, if not legal, support. The Restauration re-introduced the Church of France, but didn’t give their lands back. I’m not sure what the 1848 revolution did, but I don’t think it mattered much outside Paris.
All that to say that there was never a clean break between church and state, and still today the Church of France has more power than in many other European countries - notably in the domain of education.
I appreciate the responses so far, but I wasn’t clear enough in my question. I understand why there is the provision to continue funding the upkeep of the old churches. I’m wondering why in 1905 they ceased providing any other funding to these church communities. Seems logical from an American perspective, but why in 1905?
And, does this only apply to Catholic churches? Were there no protestant or orthodox churches in that year, or did this law simply discriminate against them? Finally, if there were no “landmark” or “monument” protestant churches that qualified in 1905, could the protestant (or Catholic) churches in areas under German control at that time qualify when they became French?
The Third Republic had a long track record of anti-clericalism starting with its founding in 1871. This was at least partly in reaction to the Catholic Church’s long-standing royallist, anti-republican stance.
According to this (somewhat confusing) site, the separation laws of 1905 weren’t in response to any one event, so much as just another step in a long series of acts aimed at reducing the influence of the Catholic Church (including breaking off diplomatic relations with the Vatican in 1904).
Also, according to the site I linked to, Protestants made up only 2% of the population in 1870 (and probably not much more by 1905), and so were not a big political influence.
I can’t find an English translation of the law, but it seems to apply to all religions, not just Catholics, although the aim was mainly to stabilize and solidify the government by reducing the political power of the Catholic Church. Remember, they’d gone through seven different governments in the past 120 years, so the fear of some group engineering an overthrow was not a far-fetched one.