Answers (2)
When he figured out that nearly all of his bureaucrats were Christians.
A ruler can not go against his bureaucrats. In China the emperor annoyed his bureacrats and they scuttled the entire navy to protect their jobs. That is why China has no history of exploring the world.
The claimed conversion of Roman emperor Constantine has long interested students of religion. According to his own account, on the eve of a battle in 312 C.E., which he won, the pagan Constantine saw a vision of a cross with the motto: “In this [sign] conquer.” He was “converted” shortly thereafter (in 313 C.E.) and brought an end to the persecution of Christians in the Roman empire. Constantine encouraged the then current form of Christianity as a State religion, and even intervened in internal church disputes. However, he also committed acts that called into question the genuineness of his conversion and was not baptized until just before his death some 24 years la ter.
While professing to champion Christianity, Constantine kept one foot in paganism. For example, he practiced astrology and divination—occult activities that the Bible condemns. (Deuteronomy 18:10-12) On the Arch of Constantine in Rome, he is
sacrificing to pagan deities. He continued to honor the sun-god by featuring the deity on coins and promoting the sun-god cult. Late in life, Constantine even permitted a small town in Umbria, Italy, to construct a temple to his family and himself and to appoint priests to serve there.