In a country where US = "bad", public US support would have been hindrance, not help. We don't know what was going on behind the scenes. Note also that the de-facto sponsor was Rafsanjani, somebody a bit too skillful to "marry unconditionally".
Obama is not a saint (he relies on the same corporate interests and even the same personnel a Clinton would), but it's hard to fault him for his moves regarding Iran.
> How do you know he didn't? Because he didn't send in bombers to "support demonstrations"?
Come on, it's quite clear that Obama was very low-key during the Green Revolution protests, much lower-key than he needed to be.