The story of the transition from Judaeo-Christians to Gentile-Christians. Jesus taught only to his fellow Jews, but the history of the expansion to the gentiles, and the discomfort between the Jewish Christians and the gentile Christians made for interesting drama and conflict.
Eventually, the gentile-Christians dominated the faith. Most Christians today were pagans in their ancestral histories - hence our Saturnalian December Christmas (Jesus likely born in April, but it doesn't really matter) - and the good old pagan Christmas trees.