In Brittany the Protestant Reformation of the 1500s took an entirely different course than that anywhere else ~ the people stayed Catholic, the nobility in the towns stayed Catholic, the rural nobles became Protestant.
In nearby France , the nobility in the towns became Protestant and the rural nobles stayed Catholic for the most part. The people split depending on social function with a Catholic peasantry and a Protestant mercantile class.
The quite large royal family at the top also split with d'Guise on one side and the Huguenots on the other ~ although even the wealthiest d'Guise had home chapels just like the wealthiest Huguenots.
When it came to foreign relations, the French relatives of the Spanish king (after 1598) fared well whether they were Catholic or Protestant.
Most amazingly in the last quarter of King Philippe I/II"S reign (1555 to 1598) the rural nobles in Brittany, then arguably the wealthiest nobility in Europe outside of the Spanish royal family, and totally Protestant, raised a sort of rebellion with a demand that their country (Brittany) be transferred from the French claimants to the Spanish claimants!
I"m working on that part right now because I find Breton nobles among the Spanish then living and working in the New World.
Their own families at the time were living in Sweden!
It's complicated.
While reducing it all to Protestants bashing Catholics or Catholics bashing Protestants may be satisfying to polemicists and apologists among the faithful of both sides, it's quite clear that this does not explain the matter in any way approaching accuracy.
Looking to loyalties to monarchy versus advocacy of a more Republican form of government does.