The article below is well investigated and describes a sad timeline of the disappointment and (justified) anger of many Iraqi Sunnis regarding the Maliki government.

http://www.bbc.co.uk/news/world-middle-east-25559872#

„Sunnis joined the first government of Nouri Maliki, but the influential posts went to Shia or Kurdish politicians and Sunni complaints of marginalisation continued…In 2007, while Iraq was sliding towards unprecedented levels of sectarian violence, Sunnis joined other secular and Shia parties and withdrew from Mr Maliki’s government in an attempt to bring him down…The gradual defeat of al-Qaeda – which turned out not to have been decisive – and the crackdown on Shia militias gave Mr Maliki significant political credibility and Sunnis rejoined his government…In the election of 2010, and apparently after understanding that they would not dominate power in the country again, almost all Sunni influential parties joined the Iraqiya bloc led by the secular Shia politician Iyad Allawi…“