This is a pretty good run down of the players but the following:

Amid the anarchy, a new kind of Shia leader emerged which no one had anticipated, and which now represents a serious threat to the rule of law in the most important Shia religious centers: self-appointed clerics who combine the might of armed militias with an almost messianic sense of purpose.....
is in a word #$%@&*&( stupid....

They have had for nearly 5 years the example of Muqtada As-Sadr to follow--who had modeled himself largely on Nasrallah of Hizballah in Lebanon for the past two and a half decades. So to say it is all a big surprise means they completey ignored As-Sadr and overlooked centuries of Shia schisms.

Best

Tom