The Internet in Ancient Times

Judaism. Specifically King Hezekiah.

And it wasn't so much that they (whoever that is) 'persecuted the originals' but that the Roman empire just kinda wiped all the other empires out.

Romans were really interested in all those other ancient empires' religions. The Hellenistic paganism the Romans adopted divided religion into three buckets: home/State-sponsored religious practices that maintained order, philosophic religious understanding and the Mysterious Religious practices. (When Classical-era Greeks would consult the famous Oracles of Delphi, this was their 'mystery' aspect)

The Romans really liked the Stately and Order part of paganism, but adopting the Greek framework left a serious wanting for the mystery part of the religion. So they adopted these much older, exotic ancient eastern cultures--Mesopotamian religions, Zoroastrian (as Mithraism) and Egyptian religions as mystery cults. Teachers would hold secret knowledge of these ancient mysteries and selectively share them with followers through secret practices and knowledge (just like the Oracles at Delphi).

Notably missing was Canaanite religion, including Judaism. The Canaanite cults had been largely state religions and were mostly wiped out by the Neo-Assyrians before Persia or Rome ever arrived on the scene. Some, such as the Phoenicians, had been Hellenized much earlier. Judaism was a weird one. Judah was a (basically powerless) vassel state to (northern) Israel who had been crushed by the Neo-Assyrians. King of Judah, Hezekiah allied with that empire briefly and looked to formulate his own state religion incorporating ideas form Israel (and thus greater Mesopotamia) He prospered for a while as a vassal state, but eventually his line tried to ally with Egypt against the Neo-Assyrians and was also crushed.

However, the people of Judah proved to be a resilient bunch and after captivity, eventually re-established their temple in Jerusalem, focusing on worship of YHWH. Prophets of Judaism added to Hezekiah's state religion and blamed their downfall and suffering on their refusal and inability to worship YHWH correctly, and exclusively.

This exclusivity eventually lead them to revolt against the Hellenistic Seleucid Empire who found the monotheism incompatible with their own paganism. Judaism was weird for a Hellenistic pagan. Jews didn't care if the pagans were Jewish or not (and still don't), their religion is about their family's relationship with the divine. Also the Jews refused to worship your gods. And they cut off the tips of their penises? There was just no appeal fro ma Greek perspective.

This led to them being crushed again, but curiously, for trying to worship YHWH correctly--opposite reason this time. This led to the development of the Messianic prophecies. The idea that YHWH was setting up the Jews for eventual independence, even if they were currently shackled. One of these Messianic prophets was Jesus. He was killed by the Romans with the blessing of the Jewish authorities.

Eventually, Jesus's followers claimed he was actually the Messiah. Also, he had somehow changed Judaism to be open to non-Jewish converts. Greeks could now access YHWH as a mystery. And also when they studied the mystery they learned he was actually the only God. This exclusivity created a situation where Christianity logically couldn't lose. Every new convert was one less pagan, but any Christian that sampled paganism was still a Christian who had sinned and could be forgiven. All this mechanism needed was a stable environment and time and the Pax Romana proved to be exactly that.

Eventually, Emperor Constantine made Christianity his own personal religion (changing the Emperor's cult) and eventually to Emperor Theodosius adopting it as the Roman state religion.