What happened to Greek/Roman/Nordic/Etc. Polytheism? Does it still exist today? How did the religions even come about and get taught? Were there religious Holy books like Abrahamic Religions have?
It does exist today, in the form of edgy neopaganism
>What happened to Greek/Roman/Nordic/Etc. Polytheism?
Jesus
>Does it still exist today?
Not in its original form
>How did the religions even come about and get taught?
Oral tradition, even the Greeks originally chanted & sung their legends
>Were there religious Holy books like Abrahamic Religions have?
No
I only know this from my endless wandering around the internet, but from what I gather they were more or less just the myths and fables that fulfilled the role of spirituality in ancient Greece/Rome.
During the early years of these civilisations they were believed more literally, but keep in mind there was no uniform idea of what actual worship/belief in these tales was and that it wasn't really as all-pervasive as the Christian/Islamic faiths that would come to replace it. You had things like the mysteries, which were secretive cults that deemed themselves to hold "higher knowledge" that only initiates would be revealed, then you had things like public worship/animal sacrifices that could be invoked for good harvests, victory in war, social recognition, etc.
As time went on and Roman civilisation proved to be a stable consistent in the world, people became less religious and instead turned began to see these stories more as just metaphors for the human condition rather than actual events.
As far as holy books go, there wasn't really any "central doctrines," but I'm sure there were plenty of treaties/religious documents that would explain the intricacies of these belief systems to those so inclined to study them.
They kind of exist today, in the form of Hellenistic and Roman revivalism, but it's hard to claim that these are the exact same belief systems as their ancient counterparts, due largely to the fact that a lot of knowledge has been lost. As far as neo-pagans go, however, they're probably among the more "authentic," since at the very least more knowledge of Greco-Roman religions exists than of Slavic/Norse/Baltic etc. religions.
Sources: Me, a drunk guy shitposting on 4chan
>>996541
All the religions that lose ground synthesize with newer faiths and become the practices of the peasant "folk Catholicism" in Italy retained priapus cults until I think the 14th to 15th century, gods in Ireland became brownies and fairies, etc...
Idk like bards and retainers of faiths existed in Europe to sang the songs of the deities like everywhere else.
>>996576
>gods in Ireland became brownies and fairies
This. Also Christianity adapted local gods and turned them into saints and shit.
BTW I read report from a German traveler that reported that even in the 17th century Greeks were in secret still making sacrifices to Zeus.
Constantine
>>996589
idiot
>>996587
Shit nigga, in Norway fishermen were still making offerings to Njord in the 18th century
https://en.wikipedia.org/wiki/Gnosticism
https://en.wikipedia.org/wiki/Catharism
tried to fuse and subvert Christianity
>>996599
>idiot
who, constantine?
>>996587
Talking of a religious paste over, in greece grottos of hades were turned in to shrines to st john