Bush's failure was not accounting for other bad actors besides Sadaam. Obama's success was a deliberate plan to promote Iran to hegemon status.
Well, I actually know the answer to my own question and it has to do with the Clown-Without-Makeup-in-Chief.
First a point of information - Don is correct in one regard about Bush 43 not fully accounting for the chaos and resultant rise of insurgency (terrorist networks) after strongman Saddam was hanged.
However, sustained military effort combined with two military surges had reduced the insurgency and the terrorist network operations significantly by the time Bush 43's administration was out of office. Deaths from terrorist attacks had declined to very low numbers and stabilized across all regions. Violence was down to record lows, oil revenue was up to record highs. Things looked brighter for the future of that part of the world than they had in centuries.
Two successful national elections had taken place and the Free Iraqi government had been formed with an effective, pro-Western, pro-U.S. leader (Maliki) in place as President.
The Bush State department team had negotiated a Residual Forces Agreement with Maliki that had only one or two sticking points left to work out (the biggest concerning giving immunity from prosecution for war crimes to our troops) when the Obama administration took over. That agreement would have left an effective close-air support and special operations force in the country (around 20-30 thousands troops, gun ships, armor and an air base) to fortify the security gains and assist the Iraqi military in enforcing order inside the country indefinitely.
When the Eightball Obama took over, instead of following the recommendations of the outgoing administration and working out the last details with Maliki using his emergency powers (to avoid going through the anti-American-infested Iraqi legislature), the Eightball DEMANDED that the RF agreement be put before the legislature knowing full well that it would be defeated (because Maliki told him that it would be defeated and begged the Eightball to allow him to use his emergency powers to resolve the issue instead).
See, the Eightball Obama, being a monstrous political pig, needed an excuse to do an immediate total pullout of U.S. forces because he was trying to score points with his pacifist, radical anti-war base. The defeat of the RFA gave him exactly the excuse he needed. Selah!
Even though the Eightball Obama administration was warned by his military advisors not to force the agreement through the legislature at risk of defeat, he did it anyway - for 100% political reasons!!!
As a result of this horrendous, inhuman travesty in failing to leave a strong residual force to support the fledgling government, a series of political avalanches ensued in the region. With the Alpha Dog gone, corruption and dissention ran rampant in the Iraqi government / military. Morale in the military collapsed. This severely weakened the new government forcing Maliki to fall back on hardline support from his own Sunni factions to maintain control of the country, alienating both the Kurds and the Shia population /government.
This caused major problems with the fragile Sunni/Shia coalition. As a result, the new government lost its influence over many sectors of the nation and they started to decline back into chaos. As the discipline of the free Iraqi military imploded, security gains also fell apart, Shia militia operatives poured in from Iran and tribal leaders once again turned a blind eye to terrorist network activity in their regions, because they no longer trusted the government to protect them.
One thing led to another and after about a year, Sunni Salafist terror networks realized that the Eightball Obama was a fully predictable political animal who would not authorize redeployment of U.S. forces to Iraq because he didn't think it was in his own political best interests to do so. So they terrorist networks put out the word around the world for all former al Queda and other Salafist terrorists to come to Iraq to continue their jihad to take over the world.
By the time the Eightball Obama was forced by political pressure to finally admit that effective international terrorist networks had returned to Iraq and that they were growing stronger and more active internationally every week, it was too late for anything but a large scale operation to reverse the gains of ISIL. The muzz terrorists boldly announced that they were no longer ISIL but that they were now ISIS (the Islamic State in Iraq and Syria) and marched across Iraq to attack Syria weakened by civil war.
The rest is history - all Hell broke loose and we are still in the midst of trying to contain ISIS and their brethren all over the world. Had the Eightball finished the process of leaving an effective residual force in Iraq instead of willfully allowing it to fail (using the lame excuse that it was "the choice of the Iraqi people" which it wasn't - it was the choice of the anti-American factions in the Iraqi legislature), ISIL and ISIS never would have gotten off the ground. The U.S. military working with the free Iraqi government would have maintained security and Iraq would likely have gone in a completely different direction and ISIS would never have become what it is today - far stronger than al Queda ever was.
The hundreds of billions of dollars in oil revenue that ISIS stole and diverted to their terrorist networks would instead have gone to the Iraqi people improving conditions there and stabilizing the government.
