Obama made the conscious decision to shove Israel into this corner for two reasons. First, because he is an egotist determined to divert attention from his domestic political woes. Second, because he is a hard-core, anti-Israel fanatic who believes that Israeli power represents the chief threat to peace in the Middle East.
The first rationale explains Obama's timing. After years of flirting with Iran -- a flirtation dating all the way back to his presidential campaign of 2008, during which he said he would engage in direct negotiations with the Islamic theocracy without preconditions - Obama culminated the burgeoning relationship with a rammed-through deal leaving Iran in control of its own nuclear destiny. Why the sudden rush? With his poll numbers dropping precipitously and his signature program, Obamacare, dragging down his presidency, Obama needed a big win.
The media duly delivered this to Obama by proclaiming his diplomatic blunder an enormous victory. Ignoring the fact that Obama tacitly gave Iran the right to nuclear development in contravention of all United Nations' resolutions and the best interests of the United States, The New York Times proclaimed, "No one can seriously argue that it doesn't make the world safer." The newspaper also called Israel's dismay at the deal "extremist" and "theater," and even admitted that the Iran deal acted as a "welcome change of subject" for Obama.
The Obama administration, meanwhile, rapidly erected a series of straw men designed to make the president look like a tower of strength rather than the appeaser he is. Secretary of State John Kerry immediately stated that those who opposed the deal thought war should be the "first option" -- an odd proclamation, given Israel's repeated desire to delay action. Obama himself said that the time for "tough talk and bluster" was over -- as though harsh sanctions backed by the threat of force were a bluff. (Which, apparently, they were.)
Though none of this explains why Obama wanted to make a deal in the first place. Yes, it was a convenient distraction -- but the president of the United States can always find a way to shift the political narrative.