By Richard Rohr, 3 Sept 2018
Much of what Jesus taught seems to have been followed closely during the first several hundred years after his death and resurrection. As long as Jesus’ followers were on the bottom and the edge of empire, as long as they shared the rejected and betrayed status of Jesus, they could grasp his teaching more readily. Values like nonparticipation in war, simple living, inclusivity, and love of enemies could be more easily understood when Christians were gathering secretly in the catacombs, when their faith was untouched by empire, rationalization, and compromise.
Several writings illustrate this early commitment to Jesus’ teachings on simplicity and generosity. For example, the Didache, compiled around 90 CE, says: “Share all things with your brother, and do not say that they are your own. For if you are sharers in what is imperishable, how much more in things which perish!” 
The last great formal persecution of Christians in the Roman Empire ended in 311 CE. In 313, Constantine (c. 272-337) legalized Christianity. It became the official religion of the Roman Empire in 380. After this structural change, Christianity increasingly accepted, and even defended, the dominant social order, especially concerning money and war. Morality became individualized and largely focused on sexuality. The church slowly lost its free and alternative vantage point. Texts written in the hundred years preceding 313 show it was unthinkable that a Christian would fight in the army, as the army was killing Christians. By the year 400, the entire army had become Christian, and they were now killing the “pagans.”
Before 313, the church was on the bottom of society, which is the privileged vantage point for understanding the liberating power of Gospel for both the individual and for society. Within the space of a few decades, the church moved from the bottom to the top, literally from the catacombs to the basilicas. The Roman basilicas were large buildings for court and other public assembly, and they became Christian worship spaces.
When the Christian church became the established religion of the empire, it started reading the Gospel from the position of maintaining power and social order instead of experiencing the profound power of powerlessness that Jesus revealed. In a sense, Christianity almost became a different religion!
The failing Roman Empire needed an emperor, and Jesus was used to fill the power gap. In effect, we Christians took Jesus out of the Trinity and made him into God on a throne. An imperial system needs law and order and clear belonging systems more than it wants mercy, meekness, or transformation. Much of Jesus’ teaching about simple living, nonviolence, inclusivity, and love of enemies became incomprehensible. Relationship—the shape of God as Trinity—was no longer as important. Christianity’s view of God changed: the Father became angry and distant, Jesus was reduced to an organizing principle, and for all practical and dynamic purposes, the Holy Spirit was forgotten.