Why did the Iranian revolt fail, where the Arab one(s) succeeded?

We remember June 2009. Pictures were brought to us from Iran of cars overturned, dustbins burning and people's faces streaming with blood in the clashes with the regime. And this continued for months. Yet, two years later, fraudulently elected president Ahmadinedjad is firmly in his saddle. Benali left.

One of the most foremost reason of a complicated situation seems to be, irony of ironies, the weight of the voice of the West.
Whereas Iran has undergone decades of embargo, and international ostracism on all levels, economical and political, the armies of Mubarak and Benali have been subsidized by the West. Especially the Egyptian military since the Camp David accords of 1979 has been able to modernize itself substantially with American money. So if President Obama of the States hardens his rhetoric on Egypt, this resounds with a significant part of the state machinery.

Secondly, despite it all, by comparison with Tunisia or Egypt in Iran there is still more popular support of the regime. Large parts of the population, especially the families of the martyrs of the Iran-Iraq war of the 80s around whom a state-sponsored cult still flourishes to this day, live well with the heavy subsidies allocated to them. There are two different armies, additionally to the Artesh, the military of the Shah's time, there are the so-called "guardians of the revolution", the pasdaran, which includes a vast voluntary section, the bassidjis. The bassidj were those in civil clothes responsible for the worst human rights abuses on the streets of Teheran in the repression of the uprising. The professional branch of the Pasdaran in their turn are heavily implicated in the Iranian economy, building high-ways and owning supermarket chains, and so have enriched themselves extensively over the past years without being corrupted.
These two armies together alone are so numerous that they constitute a powerful basis for the regime. But Ahmadinedjad also rallies the poor and religious segments of the population around him with his "messianic", millenarian discourse of the hidden Imam. In Tunisia or Egypt, no legitimating discourse was being produced at all these past years. The balance between the discontented population and the completely corrupt bourgeoisie and the dictators was one of a "pact of non-agression": As long as the populace kept quiet, the state did not kill or torture too much, with the threat poised that this could change any minute.