Mystery.
"Happy is he who, having seen these rites, goes below the hollow earth, or he knows the end of life and he knows its god-sent beginning."The Eleusinian mysteries once so secret are now two thousand years away and far from mysterious. They have been reconstructed many times from fragments left by Pinder and Aristophanes, by Herodotus and Aristotle; but like the Persephone myth, the meaning or rather the experience of it, has been stolen and buried under an obscuring layer of rational, intellectual attempts at understanding.
Pinder.
Even after the destruction of Eleusis the mysteries themselves continued, though the original mythology has been over written, updated -if you will- from Eleusis and into churches all over the world. The blood sacrifice has become communion, whilst the promise of resurrection and rebirth in the Elysian fields of Heaven remains relatively unchanged.
The basic myth has been altered to fit a new religion, it was never lost.
It would be a mistake to see the destruction of the mystery (and preservation of broken fragments of the ritual) as the triumph of the rational, though the philosophy of Plato was instrumental in this change. Plato's philosophy forms the basis for much that is considered to be *Christian* . Yet the dread of the pain and fear death brings in its wake, is not intellectual or easy to dismiss by rational argument, nor is the human desire for an encounter with mystery easily assuaged by common sense. The Eleusinian mysteries once provided a way to approach both fear of death and a desire for the numinous. Once the mysteries were abandoned the need and desire lost none of its intensity, only the original focus changed and became fragmented. I don't believe that human nature changes.
The older religions gave mystery a prime role, at times religion was entirely mystery . In Christianity mystery was given a secondary, rather than a prime role. From the Christian (Platonic) point of view the mystery religions were nothing more than cheap thrills (despite the expense!) and not religious at all; perhaps more importantly they were also competition.
Christianity had become the religion of the ruling class, God the Father had proved Himself as an efficient war-lord and Constantine embraced the simplicity of this religion in the hope of binding the disparate religions of his subjects, together. The mysteries had to go!
Christianity was so similar to the older Dionysian religion that it was able to obliterate Persephone and Demeter as the symbols and means of achieving redemption, thus Persephone was buried within in the mythology of Mary Mother of Jesus. Nor is from rape victim to virgin too large a change for Persephone as her cult, especially in its older form, required celibacy. As Mistress of the Animals, as Artemis as Potnia Theron it is not such a big step from abducted child to Virgin Queen of Heaven, paradoxical as that may seem. Persephone herself once represented salvation, she was the dread goddess of the underworld; the only one who could intercede on behalf of the dead. She was the force that impelled a soul towards bliss. Though the name of Persephone was drained of all power by Christianity, her role remains, as Mary to whom people still pray today.
In AD 364 the Catholic Emperor Valantinian had prohibited 'all nocturnal celebrations...' but the Roman proconsul in Greece (Vettius Agorius Praetextatus) had protested that without the Eleusinian mysteries, life itself would become unlivable (bios becomes abiostos) for
"The rites hold the whole human race together".So important were the Eleusinian mysteries believed to be that the famously Pagan proconsul got his way.
Thirty two years latter in AD 396 Eleusis was finally destroyed by Alaric the Goth.
The key factor to the destruction of the Eleusinian rites was the change in philosophy, rather than in religion itself. The combination of Roman rule and Christianity though formidable would not have been enough to destroy the mysteries. The will to rebuild and maintain the Eleusinian mysteries had protected them before, but this time the will had gone..
And so the Eleusinian mysteries were abandoned.