Beinart blames “hubris born of success”:
From Panama to the Gulf War to Bosnia to Kosovo, America spent the decade preceding 9/11 intervening successfully overseas. As a result, elites in both parties lost the fear of war they felt after Vietnam. In 1988 Reagan had been so afraid of another Vietnam that he refused to send ground troops to Panama. In 1990 John McCain had responded to Iraq’s invasion of Kuwait by declaring, “If you get involved in a major ground war in the Saudi desert, I think [public] support will erode significantly … We cannot even contemplate, in my view, trading American blood for Iraqi blood.” In his emotional 1991 speech opposing the Gulf War, John Kerry had mentioned Vietnam 10 times. In his 2002 speech supporting the invasion of Iraq, by contrast, he mentioned Vietnam only once.
Hubris combined with real fear. I plead guilty to both.