That’s actually a fairly complicated answer, regarding the Spanish Civil War. To my (very weak) understanding the Nationalists weren’t strictly Christians, but were definitely supported by several different Christian factions which were vying for power. It’s probably a lot more nuanced than that, and I’m just a stupid American with basically zero real knowledge of the Spanish Civil War.

Also, Christian anarchists actually aren’t that unusual. Chris Hedges, for example, is a modern one. If I recall correctly, it’s the argument that the only real Kingdom is the Kingdom of Heaven, and as such, human society should be completely non-hierarchical because we’re all sinners. Which like, I don’t believe in it, but I can vibe with that.