It lost out due to political persecution.
The OP specifies that it must be "the Roman Religion". He also specifies that it must have billions of followers and have comparable size to Christianity OTL. Once Christianity has taken control, the traditional religion isn't going to be revived. Really, all you need is for Christianity to keep the circumcision requirement for conversion (and presumably other Jewish laws which will deter potential converts to a lesser level). That's going to stop any mass-conversions that allow Christianity to grow larger. Stopping the Christian destruction of the Roman religion is easy.It would allow it to survive though... Even Julian the Apostate couldn't manage a Indigeous Roman Religion revival... general apathy was the name of the game...
I think to answer your challange that your best bet would be a misplaced stone hits Saul at the stonig of Stephen... that would hurt the Early Church big time...
Question: What sort of Roman Religions do you want large... Paganism is a pretty rubbish term... not to mention none of them would have wanted it since it essentially meant rural hill-billy...
Do you want polytheistic, monothestic, mystical cult... Take your pick and then we can make the challange a little bit more specific...
But that can't be all of it, or Christianity wouldn't have become powerful enough despite said persecution, right?
A question I have is, if Judaism could survive as an ethnic minority religion despite the heavy persecution, why couldn't Greco-Roman polytheism?
However, I still ask, what happens to the religion of Rome when Rome itself falls?
It survives, but changes through the centuries to become as unrecognizable to classical Olympianism as modern Hinduism is to Vedic religion.
I rather think the best POD for European pagan survival is actually an earlier fall of the Empire. If, for example, the central Empire was unable to bring the periphery to heel in the third century. The Church would not be able to establish its supremacy across the entire Mediterranean in just a few decades, as it was able to do later on. I think that separatism also is much easier on the maintenance of classical religion than barbarian takeovers are.
And even so, I think that without the Church having shut down the gymnasia and schools of philosophy and so forth, it will be much easier for classical civilization to survive even under the Gothic yoke. German kings will give honor to the gods at the local temples, and their sons might be inducted into choirs or be educated by the Roman leftovers (as happened historically, think of Boethius). Within a couple generations, everyone will be speaking sub-Latin and calling Arvandil 'Vesper' and Wotan 'Mercury.' The economy will be horribly wrecked, but still.
So you think they would do the standard Roman god-matching between religions to absorb the new Gothic gods? Would this merged system spread throughout the rest of Europe, or would they keep their own religions there?It survives, but changes through the centuries to become as unrecognizable to classical Olympianism as modern Hinduism is to Vedic religion.
I rather think the best POD for European pagan survival is actually an earlier fall of the Empire. If, for example, the central Empire was unable to bring the periphery to heel in the third century. The Church would not be able to establish its supremacy across the entire Mediterranean in just a few decades, as it was able to do later on. I think that separatism also is much easier on the maintenance of classical religion than barbarian takeovers are.
And even so, I think that without the Church having shut down the gymnasia and schools of philosophy and so forth, it will be much easier for classical civilization to survive even under the Gothic yoke. German kings will give honor to the gods at the local temples, and their sons might be inducted into choirs or be educated by the Roman leftovers (as happened historically, think of Boethius). Within a couple generations, everyone will be speaking sub-Latin and calling Arvandil 'Vesper' and Wotan 'Mercury.' The economy will be horribly wrecked, but still.
So you think they would do the standard Roman god-matching between religions to absorb the new Gothic gods? Would this merged system spread throughout the rest of Europe, or would they keep their own religions there?
Actually that's its main weakness. Hinduism was really just a mish mash of various cultural traditions which would be fit in at some point to help bridge the various different peoples within a polity or kingdom. For example, Ayappan has really nothing to do with the rest of Hinduism, but in Kerala, he's an important deity.Hinduism has a billion followers today and is the third largest religion in the world in spite of any missionary impulse, competition with two major missionary religions (Islam and Buddhism), and a total lack of anything resembling an overarching structure. Roman Paganism already has a leg up on Hinduism in that it has a structure which was set up and controlled by the Roman state (Pontifex Maximus and all subordinate magistracies) complete with explicit imperial support. The redirection of funds from the Roman religion to Christianity under Constantine and its elevation to the sole religion of the empire under Theodosius had a LOT more to do with Christianity's rise from significant cult to dominant religion than its missionary impulse.
Maybe I'm thinking too much of the world of Gary Jenning's Raptor (a historical novel set in Theodoric's Italy), but how about a survival of the Gothic Kingdom's Arian Christianity, and a relative weakening of Rome as the seat of what became Roman Catholicism? The Arians were supposedly less intolerant of competing Christianity denominations than either the sixth century Catholic Church or the Orthodox Christianity of Justinian.
One way to do this that might work - find a way for this guy to survive past 522-23, and Theodoric to die before Justinian's accession to the East Roman throne in 529:
http://en.wikipedia.org/wiki/Eutharic
If Eutharic took over before Theodoric got paranoid, killed Boethius and imprisoned Pope John I, you might head off the Gothic War, and leave Italy a heterogeneous mix of Catholics, Arians, Jews, and a remnant pagan aristocracy and/or rural population that follow their local traditions.
Of course, whether the Bubonic Plague of the 530's and 540's would weaken the Ostrogothic kingdom to the point that it would have been destroyed by the Lombards is an open question.
The interesting question, though, is what would happen to Roman Catholicism if it's a 'first among equals' in Rome. Does it stay centered there, or move to a more hospitable seat in, say, Merovingian France or Visigothic Spain?
Actually that's its main weakness. Hinduism was really just a mish mash of various cultural traditions which would be fit in at some point to help bridge the various different peoples within a polity or kingdom. For example, Ayappan has really nothing to do with the rest of Hinduism, but in Kerala, he's an important deity.
This could also be demonstrated through how English became so widely spoken, even while French has the Academie Française. In this case it's the lack of a central authority which helps it, not the other way around.