The early Western emperors (Europe) wanted Christian social morality to bind the Empire together without Christian theology.
Many people were "Christianized" because it was fashionable to do so.
My first thought is that we have the reverse in the U.S., ...Christian theology without social morality. But we lack both. We have eroding Christian theology, defining truth through our own reasoning and discussion, not seeking out God. And the echoing theme is an avalanche of proposed tolerance falling on the head of morality.
When Emperors made Christianity the only legal faith, new "converts" thought the worship was boring, and began introducing elements of their old pagan religions. Rituals and false doctrines infiltrated in quite disturbing fashion.
Merovingian Kings were interested in politics, their own private matters ...and immoral pleasures were rampant.
Charlemagne recognized the political usefulness of religion. If the people could worship as they pleased ...they were humble, content, and compliant. The people of faith had great tolerance, and were easy to rule, as long as no one tried to take away their faith.
This was different than Hitler and Stalin, with their strategy ...where truth itself had no place, and was considered an inevitable threat.
So, you could argue that one group was only interested in ruling, and they felt that worked best for them by letting the people have their faith. The other group felt it best to control everyone, and to persecute anyone who didn't agree.
If I lived in a country where they closed down my church, but allowed me to stand in the bread line ...I gather to say, I'd be thankful for the bread. But I go to church to worship and praise with those who look to the Bread of Life. When we compromise, we are not always creating peace ...we are often faced with tough choices, and are too soon to give up what will hurt us in the long run for the easy road of short-term gratification. The longer we procrastinate and hesitate to do the right thing, the often difficult thing ...we are only making it more difficult to do later.
Consider our freedoms ...we can't freely break the law, but our law is rapidly becoming different than God's law. Our standards differ from His standards. We can accept Jesus, and be saved, ...and as we strive to allow Him to change us, we repent of our individual sins as best we can. On judgment day, we rejoice that our name is in the Book of Life. But there are other ways God deals with us also ...He deals with nations. If nations fall away from Him, they fall. I feel we are falling away from Him ...and in many ways we are blindly ignoring the very standards He would have us uphold. We do not do this in His Name ...we do it in the name of freedom, tolerance, and our democracy. We vote what is right or wrong. It seems like God is not invited into the conversation ...He is only used as an endorsement. Even when we use Him as a reference, do we correctly reference what He's said, or would we try to change the context?