Christianity is a very weird one. For example, the Christianity that emerged in the period was what we call Orthodox Christianity, and is very different from Catholicism.
Also it excludes a lot of other religions that existed in that period and no longer exist - the various cults of the Roman Empire existed for about 1000 years during that period - for example.
Yeah and that’s as it should be. I’m on,y interested in the survivors.
Persia in particular seeded/influenced many religions but none really survive except bits of Zoroastrianism