he felt the time had come at which he should seek purification from sins of his past career, firmly believing that whatever errors he had committed as a mortal man, his soul would be purified from them through the efficacy of the mystical words and the salutary waters of baptism. Constantine despite being the major patron of the Church never got baptized until this moment. From what I understand before the era of regular confession, if you were baptized then committed a mortal sin your soul was in real trouble. Considering Constantine had his own son and 2nd wife executed, executed his brother in law, and who knows what else he took the chance to the last moment to cleanse away his myriad sins.
Considering Constantine had his own son and 2nd wife executed, executed his brother in law, and who knows what else he took the chance to the last moment to cleanse away his myriad sins.
Delaying baptism like this was apparently not an uncommon thing in that era, though obviously not something that the Church would sanction. It seems that Theodosius the Great did something similar, delaying his baptism until late in life.
Constantine's execution of his wife and son (as well as his possible motives) are covered in some detail here:
Constantine's Execution of Crispus and Fausta
And here is
another article from a 5th century source detailing the practice of Confession, particularly in the Roman Church which "carefully observed this custom from the beginning to the present time."