I know you fags sperg out whenever someone brings up non-Germanic Paganism so I will make the disclaimer:
I AM NOT A CELTIC PAGAN, I AM A GERMANIC WHO IS HEAVILY INTERESTED IN THE CELTS
but now this is a serious question, why did the Gauls collapse? Why did the Celts die out in all the lands they once held, a vast empire composing of Iberia, Gaul, Briton and even parts of Germany and Italy at one time? Why is it that the only remnants now are a few scattered nations in the English isles and a few communities in Northern France?
To first have this discussion we must dispell the myth that the Gauls/Celts were savage barbarians. They had advanced road-ways that the Romans appropriated after conquering them. They invented chainmail and the helmets later adopted by the Romans and displayed superior skill in metal-working. Their shields and swords were just as well as the Romans while being highly decorated and aesthetically pleasing. Their stone-working predated Roman stonework and was almost as skilled in realism; even what is unrealistic is very aesthetically and symbolically pleasing. Their calendars were more accurate than Roman ones and perhaps more than even our modern Gregorian calendars. They had superior knowledge of the skies and of astronomy even compared to the Germans and Persians of the time.
the lands the Celts controlled were rich and fat with resources, Spain had the most gold in Europe and France had exquisite farm-land. Yet despite all of this, the Celts were not organized as a whole or into an empire and had a very loose, decentralized form of government.
How such an advanced culture could have survived for so long with a disorganized system like theirs is a mystery, and ultimately what brought their downfall (it took far too long for Vercingetorix to organize the Gauls into a rebellion, by the time he did Caesar had already won)
why did the Celts collapse? Why were they so advanced yet so primitive? Why did they not develop any written language, or is it possible that it was lost to us or that they used a different form of language (such as the druid sign language?)
Is it possible the Celts were originally more advanced than the Greeks and Romans and somehow, over time, declined into decentralized barbaric tribes?