I kind of have a follow up question to this if I may. The New Testament makes a fairly big deal of gentiles, people who aren’t Jews and converting them. Am I correct in saying this?

If so would it be possible that it could be a partial answer to the op as well? Judaism wouldn’t spread as fast because it’s practitioners looked at it as a Jew only thing. Where as Christians and Muslims would be actively trying to spread their beliefs. This is just a question please don’t accept this as an answer op as I do not know.