So Obama should have cleaned up Georgie W's mess in 6 years, but Georgie W. is excused from creating the mess in the first place due to events which occurred almost a hundred years ago.
By the way, a prominent Republican, George Bush Sr., warned against invading Iraq:
https://www.globalpolicy.org/component/content/article/169-history/36409.html
Given their disagreement, which of the Bushes is an idiot?
Here's the problem in your thinking.
Of course, going into Iraq was a huge mistake, but the US went (under George W. Bush), conquered (Sadam Hussein was convicted and executed) and the US pretty much won the peace after 6 years after a surge in offense against the militant forces.
Obama had a choice before leaving Iraq completely, even though the Iraqi's in charge (Shiite) asked the US to leave. Obama should have insisted that the US leave a base in Iraq to protect the minorities (Christians, Yezidis, Armenians, Kurds, etc.).
There has been an on going fight between the Sunnis and Shiites. But this new group ISIS or ISIL, or Islamic State ... , has up the ante. They have been beheading, shooting all of their enemies at an alarming rate.
Obama's strategy of air strikes only will not defeat this group. For one, the air force is not sure what the legitimate targets are except for obvious targets, like the ISIS controlled oil fields. All upper echelon of the US military have said that air strikes without ground troops will not defeat this group. But Obama is insistent on his strategy, which is probably political and ideological.
The biggest problem in the Middle East was not Iraq. It is Iran, and Iran will continue to be the source of trouble. This group ISIS is an enemy of the US and Iran. Hussein acted as a buffer between Iran and the non-secular militants, which became ISIS. The US's action under Bush certainly destroyed this buffer, but in time Hussein's Sunni forces would have lost power to the growing Islamic militant forces that are threatening the West.
Both Bush and Obama have been fooled by Iran. It is not a group you would want to have nuclear weapons. The Iranians are even more dangerous than ISIS, Al Queda or any other Islamic terror group. Regarding Iran, both Bush and Obama are the idiots.