How did the Edict of Milan contribute to the growth and longevity of the Roman Empire?

The Edict of Milan made it legal to practice Christianity openly in the Roman Empire. It did not make Christianity the official religion nor did it reunite the Roman Empire. Christianity would not become the official religion for the empire until the Edict of Thessalonica. It's not until the Battle of Chrysopolis that Constantine I would become sole emperor of the Roman Empire. He would still need to reconquer parts to.