What did Mousavi want?

I don't have a good answer to this question. What did he think would happen?

Al Gore in 2000 could have made a case against the election that would have been very analogous the case Mousavi made in June. Al Gore's case would have been far stronger because he could have pointed to specific irregularities that by themselves amounted to more votes than his margin of defeat. The Supreme Court, voting along the lines of the party which appointed the Court Justice, stopped a recount of the vote with arguments that were just laughable according to most members of the US legal community at the time. The Secretary of State of Florida was an active supporter of his opponent and the Governor of Florida was the brother of his opponent.

Al Gore could easily have shut down many major US cities if instead of calming his supporters he inflamed them. He probably could have disrupted the normal operation of business in the United States for a prolonged period, and exacted a huge cost on the upcoming Bush administration.

What he could not have done was gotten a revote (even though he pretty clearly would have won if one had been held). There also was no plausible way for him to actually take office as President after the Supreme Court decision. Inflaming his supporters would have been far more likely to result in Gore's imprisonment and total political disgrace than to result in any form of success.

So why would Gore have acted the way Mousavi acted in June? What would have been in it for him?

This is a really difficult question for me to answer, and the unexplainability of this question leads me to expect that Mousavi and the political faction he represents have been severely damaged by the events in June 2009.