I'm reading a history of Christianity by DiarMaid McCullough, and it led me to wondering how the Christian belief spread towards the first 100.000 people. I can imagine what happens when a belief system reaches a critical threshold, but how does it get there? Why this specific belief system, and not any of the local or less-local competitors? (Any insights on how it went from 100K to 1M or so are also welcome of course.)
Many thanks for your insights!
My previous related answer may help you out here. Happy to answer follow-up/related questions.
If your question does not get a satisfactory answer here, you might try posting it in /r/AcademicBiblical since it's their expertise.