Two wrongs do not make a right.
1) Bush was wrong to start Iraq War, which mostly served to empower Iran and ignite ISIS.
2) Obama was wrong to pull out without keeping bases for future needs, keeping oil.
Of these two, the latter was more unforgivable, because it was truly stupid. Bush made a mistake, but I truly believe he thought the region was redeemable by democracy, given a chance. NOW WE KNOW better the true nature of Islamic Civilization.
A President simply cannot make those kinds of errors in judgement.