I have been in Iran for exactly one week covering the 2009 Iranian election carnival. Since I arrived, few here doubted that the incumbent firebrand President Mahmoud Ahmedinejad would win. My airport cab driver reminded me that the president had visited every province twice in the last four years – "Iran isn't Tehran," he said. Even when I asked Mousavi supporters if their man could really carry more than capital, their responses were filled with an Obamasque provisional optimism – "Yes we can", "I hope so", "If you vote." So the question occupying the international media, "How did Mousavi lose?" seems to be less a problem of the Iranian election commission and more a matter of bad perception rooted in the stubborn refusal to understand the role of religion in Iran.

Of course, the rather real possibility of voter fraud exists and one must wait in the coming weeks to see how these allegations unfold. But one should recall that in three decades of presidential elections, the accusations of rigging have rarely been levied against the vote count. Elections here are typically controlled by banning candidates from the start or closing opposition newspapers in advance.

In this election moreover, there were two separate governmental election monitors in addition to observers from each camp to prevent mass voter fraud. The sentimental implausibility of Ahmedinejad's victory that Mousavi's supporters set forth as the evidence of state corruption must be met by the equal implausibility that such widespread corruption could take place under clear daylight. So, until hard evidence emerges that can substantiate the claims of the opposition camp we need to look to other reasons to explain why so many are stunned by the day's events.

As far as international media coverage is concerned, it seems that wishful thinking got the better of credible reporting. It is true that Mousavi supporters jammed Tehran traffic for hours every night over the last week, though it was rarely mentioned that they did so only in the northern well-to-do neighborhoods of the capital. Women did relax their head covers and young men did dance in the street.

On Monday night at least 100,000 of the former prime minister's supporters set up a human chain across Tehran. But, hours before I had attended a mass rally for the incumbent president that got little to no coverage in the western press because, on account of the crowds, he never made it inside the hall to give his speech. Minimal estimates from that gathering have been placed at 600,000 (enthusiasts say a million). From the roof I watched as the veiled women and bearded men of all ages poured like lava.

But the failure to properly gauge Iran's affairs is hardly a new phenomenon. When the 1979 revolution shattered the military dictatorship of America's strongest ally in the region few experts outside of the country suspected that the Islamic current would emerge as the leading party.

But in Iran, even the secular intellectual Jalal Al-e Ahmad, author of the infamous Occidentosis predicted the collapse of the regime at the hands of Islamic movement well over a decade before the fateful events of 1979. The maverick French philosopher, Michel Foucault, also made the right bet as he reported the events from the street – an insight that his many admirers still shy from. Since the revolution, academics, intellectuals and pundits have predicted the imminent collapse of the regime. As of today, they have done no better.

Such anomalies can only be explained by a longue duree. Iran is a deeply religious society. Of the Shah's mistakes nepotism, autocracy, and repression were fought by communists and liberals for decades with no success, but it was his attack on the religious establishment that led to his almost overnight demise.

Since then common Iranians have applied their ideals through the ballot box. In 1997 as the ashes of the Iran-Iraq war settled and the country saw a decade relative stability, voters came out in mass to support the former president-cleric Khatami against his rival, Natiq Nouri, a senior member of the establishment. Western reporters saw this in terms of a grand generational divide: young freedom loving liberals against elder conservative clerics. But it was really a vote for the ideal of honesty and piety against allegations of entrenched corruption. Many of those same Khatami supporters voted for Ahmedinejad yesterday, despite the fact that Khatami's face was on every one of Mousavi's campaign posters.

For over a week the same social impulses of anti-corruption, populism, and religious piety that led to the revolution have been on the streets available to anyone who wanted to report on them. Ahmedinejad, for most in the country, embodies those ideals. Since he came into office he has refused to wear a suit, refused to move out of the home he inherited from his father, and has refused to tone down the rhetoric he uses against those he accuses of betraying the nation. When he openly accused his towering rival, Ayatollah Hashemi Rafsanji, a lion of the revolution himself, of parasitical corruption and compared his betrayal to the alleged deception against the Prophet Muhammad that led to the Sunni-Shia split 1,400 years ago, he unleashed a popular impulse that has held the imagination of the masses here for generations. That Rafsanji defended himself through Mousavi's newspaper meant the end for the reformists.

In the last week Ahmedinejad turned the election into a referendum on the very project of Iran's Islamic revolution. Their street chants yelled "Death to all those against the Supreme Leader" followed by traditional Shia rituals and elegies. It was no match for the high-spirited fun-loving youth of northern Tehran who sang "Ahmedi-bye-bye, Ahmedi-bye-bye" or "ye hafte-do hafte, Mahmud hamum na-rafte" (One week, two weeks, Mahmoud hasn't taken a shower).

Perhaps from the start Mousavi was destined to fail as he hoped to combine the articulate energies of the liberal upper class with the business interests of the bazaar merchants. The Facebook campaigns and text-messaging were perfectly irrelevant for the rural and working classes who struggle to make a day's ends meet, much less have the time to review the week's blogs in an internet cafe. Although Mousavi tried to appeal to such classes by addressing the problems of inflation and poverty, they voted otherwise.

In the future, observers would do us a favour by taking a deeper look into Iranian society, giving us a more accurate picture of the very organic religious structures of the country, and dispensing with the narrative of liberal inevitability. It is the religious aspects of enigmatic Persia that helped put an 80-year-old exiled ascetic at the head of state 30 years ago, then the charismatic cleric Khatami in office 12 years ago, the honest son of a blacksmith – Ahmedinejad – four years ago, and the same yesterday.

• Abbas Barzegar is a PhD candidate in religious studies at Emory University, Atlanta, Georgia