Which emperor supported Christianity and moved the capital of rome to constantinople?

Constantine the great supported Christianity. He did not move the capital of Rome to Constantinople. He moved the capital of the eastern part of the Roman Empire from Nicomedia (in northwestern Turkey) to the nearby Byzantium which was 69 miles to its west. He redeveloped it and renamed it Constantinople (City of Constantine.

The previous emperor, Diocletian, had designated Nicomedia as the imperial capital of the eastern part of the empire and Milan as the imperial capital of the western part. Milan remained the capital in the western part.