What did Constantine do that made him important?

Answer 1

Constantine ended the tetrarchy (a system with four emperors in charge) by wining two civil wars and becoming the sole emperor. Constantine issued, together with the co-emperor Licinius, the Edict of Milan of 313, which finalised the end of the Great Persecution of the Christians which had been decreed by the Edict of Toleration by the emperor Galerius in 311. The edict also provided for the restitution of Christian property which had been confiscated during the persecution. Constantine supported the Christians. He promoted Christians in the imperial administration and held synods and ecumenical councils to try to arbitrate disputes between rival Christian doctrines. He built important Christian churches. Constantine also issued large quantities of a new gold coin in an attempt to solve the problem of hyperinflation. In the long run, after his death, this worked.