I think a part of it as well is how the Roman state religion was heavily ossified at the time, and had a fair bit of power and influence that the Emperor couldn’t easily deal with. But if he converted to a new religion, it would create a new religious power structure that he could benefit from. Constantine also made a brand new capital in Constantinople, another means of moving away from the established power structure in Rome. It might have been a shrewd decision to try and consolidate his power.