European Enlightenment: The 17th century's most read philosopher produced sharp and honest literature. Yet until today the question seems to be unanswered where he really belonged (Bayle enigma).
Wiki says he professed himself to be a Protestant.
Do you have reason to doubt this? And why would the only alternative to a Calvinist Protestant be for him to be an atheist, when there were many other Christian sects and denominations?
The Stanford Encyclopedia of Philosophy states that Bayle was considered to be a skeptic in many ways. He was engaged in theological debate his whole life, but at a time when atheists were extraordinarily rare. As a son of a priest I think it's hard to believe he was an outright atheist, but he was certainly not a devout believer. He seems to be a person that was a little ahead of his time.