The Iranian Strategy in the Middle East
The Iranian people are great and intelligent people. Some of the most beautiful women are Iranian. They have a love-hate relationship with the American culture. Go there and you see it. The government knows this and tries to stifle it unsuccessfully. By the same token, the government is made up of insidious leaders who simply cannot be trusted. They are like a "car salesman", you cannot trust them and constantly have to monitor what they say to see if they mean what they say.
Of course,Iran has multiple objectives. As to the pursuit of the nuclear weapon, all they want is to move as close to it as possible by continuing to process uranium under the agreement. They already have enough refined for bomb in 4-6 weeks, if they pursue it. But for now, they are willing to agree to terms to process more for more than one bomb. All this time, meanwhile, has sanctions lifted allowing their economy to recover and gain more revenue. They are in a win-win situation. Their economy recovers while they continue to process just enough to allow them a breakout ability currently at 4-6 weeks. As time goes on, the breakout time for a bomb will shorten.
Iran wants to be the regional power, a Shiite power to take on the Arab Sunni countries. America is helping them with their "hands-off" policy in Syria and now Iraq. This helps Iran further entrench in both countries via all sorts of aid programs to win the hearts and minds of the locals. Hezbollah helped Assad in Syria win, as did the Iranians by sending troops their with little opposition from the West. The Free Syrian Army is mostly gone now, replaced by a bold al-Qaeda force, ISIS, now establishing their "country" within Iraq by seizing the cities of Fallujah and Ramadi. Unless Iran provides direct aid to Iraq, there is little hope the Iraqi forces would be able to oust them. The US and Iran are oddly on the same side, for different reasons, when it comes to al-Qaeda in Syria and Iraq. Both view them as the enemy.
Iran would love to further put Iraq in their sphere of influence. The Shiite Iraqis know this, yet if they are unable to, they need to help from somewhere. The Saudis are Sunni, so it will not come from them. Again, Iran is in a position to win more kudos in Iraq by providing aid to Iraqi forces to deal with al-Qaeda.
The US policy is one of sitting on the fringe and doing little.