Obama made it clear in his 2008 campaign that he will speak to America's enemies with no preconditions. He made it clear in those early days that a more perfect Union should not be the enemy of the good, meaning that any measure (think Obama care for instance), while flawed should not be abandoned once it leads to somewhere.
That, combined with his quote of the use of the power of American example rather than the example of American power make him an ardent disciple of diplomacy.
He was brilliant in bringing Iran to its knees with getting allies with much to lose to enforce crippling sanctions.
He unleashed Stuxnet which set back Iran's nuclear program. He got the Saudis to keep pumping oil while got lucky with US gas that kept oil prices low.
So you see no military action, and Iran's nuclear ambitions are put on hold.
With the Iranian population seeing possibilities the Mullahs could change.
Heck Obama could even start a Saudi-lranian Sunni-Shiite rapprochement.
Israeli-Palestinian peace next?