In the first century the followers of Jesus were called Christians, not Catholics. They were mainly Jews, some of them in Palestine, but others in Asia and elsewhere. Along with those Jewish Christians there were an increasing number of Gentile Christians joining the faith. And in the centuries that followed, as a result of missionary endeavors and forced emigration as a result of persecution, the gospel spread all the ay to Britain, Africa, across Europe and into the far east. There were no denominations, they all had one faith, and their only leader was Christ. As the church grew, it was necessary to organize and oversee church business. Charities, mission, supporting one another under duress, etc. So from early on they appointed by popular vote, bishops and deacons to look after the flock. Others who had special gifts were to evangelise, others to shepherd the flock, etc. In certain areas such as Arabia, where the church grew to such an extent that it covered thousands of miles and had hundreds of thousands of members, where the bishops were numerous and had massive areas to cover, there was appointed a metroplolitan. But all those overseers, of whatever station and responsibility, were equal in rank...they were all brothers. NOne lorded themselves over others or demanded any other to a position of obedience and subjection. Not until Constantine vacated Rome for Istanbul, which he renamed Constantinople.
In Rome there was left a vaccum. Over time, the Roman bishops came to a point where they lusted after the civil power, the secular authority, and the baubles of office that came with that worldly status. The fame, the importance, the social status. By the 6th century, such was this status entrenched into Roman society, that it became officially recognized by the eastern emperor, Justinian. Thus it was a falling away from the purity of devotion only to Christ, to a lusting and competing for political power by what was at one time a true church, that brought about what we now know as the Papacy...the Catholic church. By placing faith and trust in political power and the strength of arms to defend the church and its members, the church in Rome went into apostasy. For some time she had been incorporating the symbolism and traditions of paganism, but this taking over of the civil power was the last straw that divorced her from her Husband, and she became a whore. The following steps further into deeper apostasy came quickly. She used the state and its weapons of warfare to further her grasp on power throughout the following centuries, until such time as she controlled all of Europe. This was the Catholic version of "sharing the gospel". Such was the rise of Catholicism, and the demise of Christianity, in the Roman church. Oh by the way. And Christianity elsewhere? Well, it wasn't long before they became a thorn in the side of the Roman church, and thus it was necessary for Rome to paint those churches in the darkest shades of grey possible, justifying persecuting them, and destroying them by labelling them as "heretic" and lying about their beliefs and practices. Altering history and destroying the written works of those Christian communities became standard practice from Rome to Britain, and everywhere in between. Islam took care of the rest. The connections between Islam and Rome...well, that's another story.
