I feel Christianity was not the cause for spiritual decline of Rome. Many factors contributed to the growth and expansion of the church, and ultimately its success. Rome did not welcome this new religion with open arms right from the start. Some emperors, like Marcus Aurelius openly rejected Christianity numerous times. Once Christianity was welcomed and even encouraged, many people followed their emperor’s lead and embraced this new religion.
The first of the reasons that the Christianity spread was a political factor. Rome was a dominant force in the world at this time and had excellent roads and shipping, which made it easy for missionaries to travel and spread the word of the gospel. This travel and preaching was easy because there was never a continuous policy against the Christians and no imperial edicts were ever decreed. There fore the missionaries cold travel relatively safely in times of little persecution.
Another political factor would be the Pax Romana. This existed between 27 BC and AD 180, it was along period of relative peace experienced between the states of the Empire. This allowed the interior states to remain relatively unscathed by warfare and gave the Empire the outwardly appearance of peace. This proved advantageous for missionaries as they were almost guaranteed security while traveling.
Christianity’s attitude towards society and its social impact also lead to the expansion and success of the church. The church was particularly well known for its acts of charity. The church offered this charity to everyone, including pagans. By the third century the Church was looking after one thousand five hundred widows in need.
They were also socially accepted, in some areas, because of their courage during the persecutions and the strength of their faith and the support they showed one another,