Christianity spread in many different areas, for many different reasons. It is simplistic (and in many cases wrong) to assume that it only spread because 'men of power' converted, though that certainly did occur. By the Mongol Invasions as many as 1/3rd of Christians lived in areas that had never had Christian rulers, and as many as 1/2 lived in places that did not have Christian political elite. Many historians (but by no means all) believe that there is enough evidence to suggest that Christians were disproportional uncommon in their nation's armies up until the fifth century, so it certainly was not because rulers wanted their martial strength.
Christianity certainly did encourage many disposed to join its ranks. In particular in appealed to women. In the Roman Empire in the second century there were 70-75 million people; of these, 25 million were women. This is because infanticide was particularly common, as it is in most agricultural societies (females, on average, produced far less food than men, which encouraged their parents to kill them as children before they began to take up resources). The Christian community effectively went to war against infanticide and were well known for digging through trash pits looking for babies and begging from door to door for people to give their unwanted children to them.
Also it can be argued that the conceptualization of the modern charity organization originates with the Christians in Rome. Julian (known as the 'Apostate', which I think sounds pretty awesome) was known to lament how the Christians take care of not only their own but the pagans as well- this line of thought was not knew to Julian, but had gone on for at least a hundred and fifty years before him.
There is a current trend of thought in historical circles that the conversion of many pagans to Christianity was similar to the Christians conversion to Islam latter, in that it was mostly a cultural diffusion rather than outright violence. Less charitably outright violence certainly did occur, in the Roman Empire and elsewhere.
As for Constantine, it seems he began to believe that Sol Invictus was another characterization of Jesus Christ. Many Christians did as well- as late at the 7th century Christians in Rome prayed looking at the sun. That is (likely) why Christmas is set on the birthday of Sol Invictus. His conversion was not as set as many here seem to believe anyways.
Christianity certainly did encourage many disposed to join its ranks. In particular in appealed to women. In the Roman Empire in the second century there were 70-75 million people; of these, 25 million were women. This is because infanticide was particularly common, as it is in most agricultural societies (females, on average, produced far less food than men, which encouraged their parents to kill them as children before they began to take up resources). The Christian community effectively went to war against infanticide and were well known for digging through trash pits looking for babies and begging from door to door for people to give their unwanted children to them.
Also it can be argued that the conceptualization of the modern charity organization originates with the Christians in Rome. Julian (known as the 'Apostate', which I think sounds pretty awesome) was known to lament how the Christians take care of not only their own but the pagans as well- this line of thought was not knew to Julian, but had gone on for at least a hundred and fifty years before him.
There is a current trend of thought in historical circles that the conversion of many pagans to Christianity was similar to the Christians conversion to Islam latter, in that it was mostly a cultural diffusion rather than outright violence. Less charitably outright violence certainly did occur, in the Roman Empire and elsewhere.
As for Constantine, it seems he began to believe that Sol Invictus was another characterization of Jesus Christ. Many Christians did as well- as late at the 7th century Christians in Rome prayed looking at the sun. That is (likely) why Christmas is set on the birthday of Sol Invictus. His conversion was not as set as many here seem to believe anyways.