Bush had excellent reasons for invading Iraq, which he stated at length.
He created a democracy in the Middle East. Not a shining democracy, but Iraq became a country where the people could self-determine and not be casually brutalized by Saddam’s gangsters. When Bush left office Iraq was the least worst country in the region (except for Israel of course).
The subsequent abandonment of Iraq is NOT a natural result of a rich country getting bored: it is the result of vile left-wing treachery. Just like Vietnam.
The fact that the American Left has a habit of betraying America’s allies is not something to reproach Bush with. The squalid know-nothings who voted for Obama - twice! - bear the shame for Iraq.
The post-invasion Iraq officially became a farce when the U.S. leadership allowed the new Iraqi government to adopt a constitution in which Islam is enshrined as the official state religion. That pretty much guaranteed two things: (1) Iraq would remain culturally dysfunctional in perpetuity, and (2) Iraq would be an unstable mess due to the competing interests of various Sunni and Shi'ite Muslims.
The problem here isn't that the Bush administration did something wrong. The problem is that the Bush administration fouled this up even though anyone who looked at the situation objectively and wasn't viewing it with a political agenda in mind was predicting exactly what we're seeing now. As I've said many time here on FreeRepublic, Iraq is a disaster today because Saddam Hussein was far more effective at quelling civil unrest and radical Islamic extremism than anyone in Washington.