One important thing to remember when we talk about “the” Church as it existed in “the” Empire, during the 1st, 2nd and 3rd Centuries, is that the two, while they existed in the same space, were not the same thing. Nor were they even very much alike. In fact, they were directly opposed to one another, most of the time, and the Church never knew when a new wave of repression and persecution might break out. Even in times when Churchmen had an “in” with the Emperor, himself, that same Emperor might, for political reasons, get up one morning and order that every Bishop in the Empire be arrested and tortured, and all his books and papers seized and burned. It happened more than once. Indeed, it happened just about every twenty years, on average.
Now, twenty years is a long time. In twenty years, given good communications and easy travel, a Church can grow from just a handful of persecuted slaves and peasants into a large and thriving congregation! It took a long time to hand-copy the whole Bible, but if the work was spread out over several congregations, and one person only had to copy one book (or a part of one), then within a year or two, most congregations could put together a pretty complete manuscript. If this could then be shared, then re-establishing the stock of Holy Scriptures after even a major persecution probably didn’t take very long. The same was true of the buildings. At first, the meeting place would have been homes. Later, they would start to move into public venues, like cemeteries, and within a few years without overt persecution, they would start building buildings. This frequent tearing down and re-building had several implications for the young Church.
First of all, the recurring waves of persecution was highly destructive of higher leadership. Had there been one man (or woman) at the “top” of an Empire-wide Church, he (or she) would have been seen as a threat to the Emperor, and would have been gotten rid of. So: the Episcopal form of Church governance grew up. In the earliest days, every separate congregation probably had its own Bishop (in Greek, “episcopos”; see Acts 1:20; I Timothy 3; Titus 1; I Peter 2:25, for examples), but since the Romans habitually came for the Bishops first, it became the standard practice early on to have several congregations, each led by a presbyter, or “elder”, subject to one Bishop. Bishops could, and did, move around from Church to Church. Still, there is no evidence of any higher level of Church leadership than the Bishop. The Church was local. They all eventually worshipped pretty much the same way, but their leadership was strictly local. This spread the power of the organization very, very broadly: the exact opposite of the way the Romans organized the Empire.