This says it all right here, folks.

[wnylib]

29. For most of human history,

religious, cultural, and political identities were intertwined, and nearly inseparable, beginning with tribal societies whose religious practices were experiential more than ideological.

Forced assimilation of conquered people included adoption of the conquerors' customs and laws, which inevitably meant religious conversion since religion was a cultural/political identity for unifying members of society.

Greeks installed images of emperor gods in the Jewish temple, sparking a Jewish revolt. Rome acknowledged Judaism as a tolerated religion (having observed what happened when the Greeks did not), but Jewish revolts against Roman rule brought severe punishments. Roman toleration of Judaism did not extend to early the Christian sect of Judaism when it became a separate religion of its own, which was based on a Jew who had been executed for treason.

Much earlier, Babylon tried to enforce suppression of the religious practices of its captive people, including Jews. Judaism picked up aspects of Babylonian religion from that period. The liberation of Jews by Persia to return to their homeland and reestablish their political/religious identity was an exception to forced conversion by a conqueror, but was politically expedient in gaining cooperation and forestalling rebellion. Judaism absorbed some of Persian Zoroastrianism during that period, including the Jewish messianic version of Zoroastrian end times beliefs.

Early Christians could escape persecution and have their other religious customs tolerated if they agreed to pay lip service to Rome by also celebrating sacrifices to Roman gods, but Christians refused because that violated their core beliefs.

Emperor Constantine, a "sort of" convert to Christianity, initiated the demand for a Christian orthodoxy to condemn other branches of Christianity as heretical in order to have a single cultural religion to unite his empire. The merging of Christianity with the politics of Rome carried into Roman conquered lands and remained with Christianity under Roman religious leaders and an established identity as a Roman religion when the words "Roman" and "civilization" were synonymous.

But in all periods in various religions, there have also been people whose focus on religion was spiritual and philosophical rather than political. That's the nature of human beings. Political leaders use religion for their own ends, and the common people split between political followers and the politically ambitious versus spiritual/philosophical followers of a religion.