Failing to persuade
Asking why Mir Hossein Mousavi didn't win Iran's election is like asking why Meretz or Labor didn't win here. Iranians, like Israelis, don't vote as they do elsewhere. True, many Iranians aren't satisfied with Mahmoud Ahmadinejad, but as in other places, things depend on the alternatives.
In Ahmadinejad's favor, he was the incumbent. In Iran, a president finishing two terms is based on his control over the government apparatus, a huge budget and wide media exposure.
Ahmadinejad appointed a supporter to oversee the election, making sure it went his way. Through the state budget, he won support in all sectors. In May, Ahmadinejad decided to pay monthly bonuses to civil servants, and junior religious officials recently received a booklet on the regime's achievements with a check enclosed.
But corruption alone doesn't explain the big victory. Ahmadinejad also represents poor people and villages, far from Tehran's power. He's not a religious scholar but is associated with conservative thinking. Although he's a controversial figure among many religious scholars, most didn't find the other candidates, including Islamic scholar Mehdi Karroubi, a fitting alternative.
It is assumed that reformist Mousavi won over young voters, who hadn't experienced the Islamic revolution and whose complaints about Ahmadinejad relate to education and freedom of expression, and especially jobs. But it seems that even here, Mousavi wasn't persuasive about his ability to effect real change.