Constantine the Great allegedly converted to Christianity, but there is no evidence that this is true. There is far more evidence that he continued his pagan sun-worship religion but now in a modified form with Christian names, terms, and ideas applied and symbols blended in to give it all a certain “Christian” flavor. But only the ignorant would not be able to see the difference. They knew that Satan had played a trick. They knew that there could be no compromise. They loved Jesus and continued to keep his commandments.
In other words, only Christians who saw a personal benefit from leaving the real thing for the counterfeit, would swap. And there were indeed many advantages to Constantines Christianized paganism because he did many things to make his the new state religion appear advantageous and attractive. He offered lots of money and wealth and prestige to the church. He erected big buildings to the church. And another important thing was that if you swapped from the original Christianity to the pagan counterfeit you were suddenly free from persecution and could be integrated into society. You moved from an outcast to becoming a member of a prestigious, rich club.
Remember that true Christianity was an outlawed religion in the Roman Empire. Why that? Because the pagan sun-worship religion (both in its pure pagan version and in its Christianized version) required that you paid homage to the Emperor as to a god, and also acknowledged the pagan view that there are many gods (polytheism). But the Christians only believed in one God and one Lord, Jesus Christ. They would not worship the Roman Emperor or pay homages to the many different gods. They shared a monotheistic view of God with the jews, and that was not a popular thing in the Roman Empire. So in particular, true Christianity was a despised religion and many simply wanted the Christians to be wiped out from the Empire. But even severe persecution had not got rid of them. Christianity still continued to spread despite persecution and its status as a subversive sect that made it very difficult to be accepted in society and have an income.
But of cause, a lot of people who were connected to the true Christian faith – for example by birth – were either deceived by Constantine’s ideas or they just calculated the benefits by swapping. The ones who were deceived are somehow excused because it all started with a public declaration that declared that persecution of Christians should end in the entire Roman Empire. At that stage, I guess no Christians could see-through this satanic trickery, that it would only be the first step in a direction that later ended in the most inhuman perecution history had ever recorded. At that stage, it was impossible to know. Christians were happy and definitely saw this declaration as a giant victory for Christianity.
He did was is so common for people today: They go “shopping” in all kinds of religions and philosophies and take bits and pieces that suit their preferences. That is what Constantine did. And isn’t that okay? Well yes. Unless you are an emperor in an Ancient Roman Empire and you make a law that this is the new state religion which all people must follow by law…or else!
For a non-believer, it must seem very sectarian and arrogant to claim such a thing that a particular individual or denomination is a true Christian, and another is not. What an arrogance to set oneself up as a judge in such matters, you might say. It might be such a claim that makes people think religious people and religion as a whole is the root of all evil.