Final answer:
Christianity became a major religion in Australia with the British settlement and was facilitated by the gold rushes of the 1850s and the law ensuring freedom of religion. It follows a history of growth from a persecuted faith in the Roman Empire to becoming the official state religion under emperors like Constantine and Theodosius I.
Step-by-step explanation:
Christianity was established as a major religion in Australia following its settlement by the British in the later end of the 18th century. With the establishment of penal colonies and an increase in European immigration, particularly during the Australian gold rushes of the 1850s, Christianity became the predominant religion. This was further reinforced by Australian law, which upheld the principle of freedom of religion, emphasizing that there would be no national religion in the country. Early on, Christians in the Roman Empire, including parts of Africa and Asia where the influence was considerable, disapproved of practices such as animal sacrifice and emperor worship, favoring prayer and meetings in house churches. As the Christian population grew and began to gain support from imperial figures like Constantine and Theodosius I, it started to transition from a persecuted sect to the official state religion of the Roman Empire. It was in this environment, not just in Rome but also spread across its vast territory, that the foundations of Christianity as a major global religion were laid.