None of the Arab-Spring populations had democratic rule since, arguably, Carthage. Iran is different [1].
More importantly, Iran was recently a secular society. It has memory of education and freedom. Many Arab countries have been fundamentalist for their entire modern eras.
(To be clear, every first democracy arose from the ashes of a string of fallen autocrats. I'm arguing for Iran being different from Egypt, Tunisia or Gaza.)
[1] https://en.wikipedia.org/wiki/Democracy_in_classical_Iran