I'm not so sure. The selfsame fact that this idiot is a diaper stain, and still commands the awe of such a large bunch of misfits tells me that were he whacked, any other dim bulb would stand up in his place.
Killing him means playing active whack-a-mole. Leaving him allows the flies to gather in a convenient place.
At the beginning, I believed Bush's theory that all people crave freedom. At this point, I think Mohammad was faced with these people in his time and came up with the only way to keep them in line.....busy praying and cut their heads off if they look askance, and promise them goodies in the next life knowing they were screwed in their current life.
Freedom and liberty is dangerous for people who have no good options.
I think Maliki knew all about the operation, but he's claiming he wasn't consulted so he can still try the diplomatic approach with Sadr, i.e. good cop/bad cop.