RE: The historical connection (at least in my view) was never made between the rise of Christianity and the fall of the Roman Empire.
Rome fells hundreds of years later after John died.
Constantine the Emperor converted to Christianity ( and most of Rome with him ). In 313 Constantine issued the “Edict of Milan,” which commanded official toleration of Christianity and other religions.
I’d suggest the History Channel to continue with the HISTORY OF CHRISTIANITY. Now, that would be a worthwhile project.
Indeed it would, but I am not holding my breath. The HISTORY/Hitler Channel has a notorious "history", along with NatGeo Channel, of presenting bunches of episodes about Christianity presented from "The Jesus Seminar" POV over the last decade. If not familiar, do a Wiki search on "TJS". It boils down to a group of theologians, going back to the 1980s, who decided that Jesus was not divine.
The HISTORY/Hitler Channel has done many excellent and interesting episodes on Hitler, but where oh where are the series on Stalin, Chairman Mao, and everything commie? I would very much like to see a series done from the 1997 book, The Black Book of Communism.