If we take the PurANas as being allegorical tales, then it may be asked here: who wrote them?
I wrote them after chillin' with some females in Madurai.
Before start answering this question, we will do well to notice one important fact that the Vedic Deities are no more considered as Gods in the PurANas. What were the Vedic Deities once became mere names, of many JivAs (enlightened/ exalted/ ignorant souls), and thus dissolved into insignificance. SavitR, BrahmaNaspati, Aditi, Sudhanvan, Indra--- all these transformed into just words, or at best were conserved through attaching some harmless connotation (Aditi thus denoting the name of the wife of certain Rsi), or worse still, by making a formal mockery of the words (Indra, "the corrupt demigod", being a case-in-point, or even Daksha).
I, and neither the Shri Vedic Gods, forgive for such a corruption. It seems that they have discarded their protection.
That their coming into existence is pre or post Vedic is arguable, but what can be said with some certainty is that the PurANas were not originally the creations of priests or elites, as they were more engaged with the "high brow" theories of "Brahman", "Moksha", "NirvANa", "bhedAbheda", "chintyAchintya", and so on. On one hand these elites were unable to come to terms with the Veda, on the other they felt threatened by the seeming chaos of Hinduism that was practiced on ground- a riot of innumerable PurANic Gods and Goddesses.
It was because of self-appropriation. Many of these add-ons were in response to the vast multitude of Gods in their expanse. On one hand, they had to respond to the monotheistic, invading Persians, then on the other hand, they had to (years down the line) respond to the fools persuaded by Thomas' Patrons, and then the ultimate redaction started to occur around 700CE with the Muslim influence.
Manish: Oy, Sunil! Bring me a few copies of those manuscripts!
Sunil: Why boss?
Manish: Because, we have to make it look like we are monotheist so we may not get killed.
Sunil: But, why do we have to be cowards? Why can't we be like the societies of the Rig Veda where those guys didn't take crap from anyone?
Manish: .....
Manish: (ignoring the question) I don't want to get killed, so let's alter a few Vedas and a few manuscripts here and there so we can fit in.
Sunil: .....
Veda was a secular religion, it will come back to the centre stage in a future, no doubt about that also. In the meantime, I dare say, PurANas became the Veda de facto. And they were created by "common folks". They were the Rsis of the Kaliyuga, the illiterate ones who went around places singing the songs of various Deities.
I wonder what Rishi Grtsamada, Rishi Vishwamitra, and Rishi Vasishtha would have said if they compared the Samhitas with the Epics - and even with the Puranas. I doubt what they say will be good.