> I mean, how many societies have a religion centered around some other ethnic group?
Plenty. Southeast Asia has religions centered around Indian or Arab religions. Same for Iran and much of Central Asia with Islam.
All these places have adapted the other ethnicity's belief system to their own culture.
It's no different for Christianity. Bertrand Russell described it as the combination of Greek philosophy with Jewish mythology and Roman societal/power structures.
I want to add double emphasis on this. Christianity before and without the Greek philosophical influence is primarily a religion of itinerant ascetics and martyrs (without the abstract ideals added, almost all of the story in the Gospels boils down to an itinerant ascetic being martyred).
Some of the earliest extant texts in Christianity come from Justin Martyr, who, just a century after Jesus, was already workshopping the idea that Plato and Socrates were unknowing Christians that laid a philosophical ground for Christianity.
For an intriguing spin on this, look into Manichaeism, a 3rd-century religion from modern Iran which syncretizes Zoroastrianism, Christianity, and Buddhism, and survived until the middle of the last millennium in China.
Plenty. Southeast Asia has religions centered around Indian or Arab religions. Same for Iran and much of Central Asia with Islam.
All these places have adapted the other ethnicity's belief system to their own culture.
It's no different for Christianity. Bertrand Russell described it as the combination of Greek philosophy with Jewish mythology and Roman societal/power structures.