The dominant discourse as of late about Iraq has been the opportunity for those who opposed the Western intervention in Iraq to gloat, to repeat the largely vacuous claims that the war was "illegal" (when it was legally authorised by the governments concerned and to grant any legal status to the psychopathic Saddam Hussein regime is to abrogate any notion of needing law at all) and to blame the recent ISIS successes on Tony Blair and GW Bush.
The grain of truth in that is important, but it is not the key point at this stage
It is true that whilst the West was very capable, with aplomb even, in overthrowing the Hussein regime, and indeed few think that was bad in itself (although Saddam Hussein's chief sycophant George Galloway thinks so, but he has since gone on to lick the blood stained boots of Bashar Assad and Vladimir Putin), but was woeful in establishing a new order and constitutional framework on Iraq. It was completely morally correct to overthrow the regime, which itself broke international law across many fields (international aggression, use and development of weapons of mass destruction and human rights) and was egregiously evil. However, to expend over US$1 trillion in taxpayers' money and thousands of Western soldiers lives and not have an effective plan for a peaceful future (except for the relatively successful Kurdish region, which had spent over a decade effectively protected by a UNSC endorsed No Fly Zone), was grossly negligent.
It is for that, that Bush, Blair and the supporting leadership of those administrations deserve to be damned.
Let's be clear, had the bulk of Iraqis been imbued with the belief that all other Iraqis, regardless of what sect of Islam they followed (if any) or their background, deserved to live their lives in peace, then it would have been easy.