I once read that empires spreading their religion and culture through force was a not the most effective or common method. The way it usually worked was that once conquering foreigners became the elites in society, people in proximity to the elite would adopt the culture of their superiors, to fit in. Once a critical mass of elites and their subordinates adopting a foreign culture/religion was reached, it spread throughout society like a trend.
Anyway the point I’m trying to make is the power of proximity to the elite is enough to overrule a person’s whole identity. Anybody who’s close to a a social climber will recognize how this works.