Iran sees its coming influence and slice of the oil pie in Iraq after America cuts and runs
We will exit and Iran will step down from its nukes, that's the deal
to politically justify the exit, there has to be fewer attacks on our troops
this can only be accomplished by Sadr reining in the elements he controls
his orders for a cease fire have come from Tehran
he can now use American forces to purge his own ranks that have fractured and who are refusing to obey him, plus he will provide Intel on AQ
he will fully consolodate his power and be a minor Iranian Caliph in Iraq, though his luxary will never equal or come close to Saddam's
We never killed him because we knew Iran could and would at any moment if necessary

There is a real puppet master in Iran the likes the world hasn't seen in a couple of decades and it ain't Iran's President. Sadly his power has come from the clear dissent amongst State, DOD, CIA and the Presidency. Not one freakin' time were 3 out of the 4 on the same page in this war, the prerequisite for strategic implementation. As Bogart would say, " play it again, Uncle Sam"