Final answer:
Christianity became the official religion of the Roman Empire through the Edict of Thessalonica in 380 AD, following the Edict of Milan in 313 AD that granted religious tolerance to Christians.
Step-by-step explanation:
In 313 AD, Emperor Constantine issued the Edict of Milan, which granted religious tolerance to Christians. This was a significant turning point for Christianity in the Roman Empire. Later, in 380 AD, Emperor Theodosius I declared Christianity the official religion of the Roman Empire through the Edict of Thessalonica.
This decision was influenced by several factors. First, Christianity had gained significant popularity and followers within the empire. Second, the conversion of Emperor Constantine to Christianity and his vision of a Christian symbol before a battle played a crucial role in its acceptance as the state religion. Lastly, political and cultural reasons, such as the desire for religious unity and control, also contributed to the adoption of Christianity.
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