FearGod
Freedom Of Mind
Good question. I have opinions, but that is a more details question. Likely @outhouse has a much better informed explanation of Constantine's personal life.
One thing Muhammad apparently learned from the Christians is how much better it is to say that you are improving an old religion. Rather than say that you are inventing a new one, even when you are.
Tom
Why a powerful rich warlord was in need for the old religion, i think the old religion has to be in need for the powerful warlord.