Constantine grew up in a home where his Father was very tolerant of Christians. This probably had much to do with his later life decisions. In 312 Constantine, before the battle of Milvian Bridge near Verona, has a vision in which he believes God shows him a symbol that will bring him victory against his opponent Maxencius. Constantine puts this symbol on the shields of his men and the flags that he bears and wins the battle. After this battle Constantine adopts Christianity as his own persona faith. While there is evidence on both ends of the spectrum for whether or not he was actually a Christian the truth can only be known by God.
In 313, Constantine issues the Edict of Milan in which he granted tolerance to Christians. In the short term, this ended persecution, at least from the political perspective and Christians were treated as equals in court and other legal arenas. Social however there were most likely still some persecutions taking place. In a modern context one my think of the civil rights movement.
In 323, Constantine proclaims himself as the Sole Ruler / Roman Emperor. He makes Christianity the preferred religion of the decade and sets up a theocracy in which the church rules the state. Constantine considered himself as the bishop to the bishops, which in some cases portrayed a very negative picture of Constantine as he took his authority a bit to far. He began to give every soldier that would convert to Christianity 20 silver coins. Think about going out on a street corner and announcing that anyone who would accept Jesus Christ as their savior would be given a $50 bill on the spot. This would indeed be a stimulus package!
In the long term, Constantine brought the Church out of an era of persecution. Not everything was perfect in the beginning but it was a major start in getting the church a voice again. However this voice in later year will become over dominant and become the persecutor rather than the persecuted.