Obama: “Iran will not get a nuclear weapon on my watch”

How did we go from Iran never getting a bomb, to Iran not getting one during the last 18 months of Obama's Presidency?  That's basically what the President told the New York Times when he said this is a "once-in-lifetime opportunity" and that “Iran will not get a nuclear weapon on my watch”.  Who's lifetime is he talking about?  The shortened Israeli's lives that might end after Iran nukes Israel in the days or months after Obama leaves office?  In 2012, he made it crystal clear that he would stop Iran from ever getting a nuclear weapon.  Of course, 2012 was an election year and now he's never going to run for office again.

These words clearly show that Obama lied in 2012, and they clearly prove that he doesn't have Israel's back or, for that matter, the world's back with this pending Iran nuke deal.

References:

2012: Obama's Crystal-Clear Promise to Stop Iran From Getting a Nuclear Weapon:  http://www.theatlantic.com/international/archive/2012/10/obamas-crystal-clear-promise-to-stop-iran-from-getting-a-nuclear-weapon/262951/

 Obama: Iran Deal ‘Once-in-a-Lifetime’ Chance:  http://www.voanews.com/content/obama-iran-nuclear-agreement-a-once-in-a-lifetime-opportunity/2708079.html