"evolving theology," neat expression, Pete.
And, I agree that evolving theology meant that previous doctrine could become a reason for 'death,' in the sense of spiritual death, (smile) and prison and even death - a very real threat if the local bishop and the state were on the same wavelength. And it was not just those who adhered to traditional pagan beliefs that could face death under the new theocratic state, but quasi-jewish/christian groups like the Manicheaens could also face death.
Back in the first days of this new religion, the first Christians, Jews who may not have even thought of themselves as having left Judaism would likely have had a difficult time seeing Jesus as 'god' - but the later converts - so-called pagans who had a prior belief system in which they had accepted and believed that the Emperor could be a god, would more easily accept Jesus as god.
Even so, defining the difference between 'god the father' and 'god the son' caused some unholy rows in the church. If you can find a copy of Colin McEvedy's, The New Penguin Atlas of Medieval History in your local bookshop or library, you can visualise the splits by a map on p.23, and accompanying text. By this time, says McEvedy, Church and state had fused to form a new society. And, in that fused society the Church tightened its grip on both the Emperor and his subjects, and it was NOT a kingdom of love.
Robin Lane Fox's great study on the beginnings of Christianity (Pagans and Christians in the Mediterranean World) comments in the chapter on Constantine and the Church, that Constantine by 324, had learnt that, " not even the fear of God's vengeance could force Christians to agree."
The interesting point on McEvedy's map, which shows Christendom in 528 CE, is that the Pope ruling in Rome on the imperial pattern, and essentially holding to the what we might call the trinity, was surrounded by a sea of churches which accepted Arianism. We can imagine the result.