Summary of Jared Diamond's Collapse.
First, he argues that sometimes societies fail to anticipate an emerging problem because they lack adequate knowledge or prior experience with the phenomenon at hand.
By analogy, one could argue that some recent failures in U.S. foreign policy were of this sort. Hardly anybody anticipated that U.S. support for the anti-Soviet mujaheddin in Afghanistan would eventually lead to the formation of virulent anti-American terrorist groups, in part because the U.S. leaders didn't know very much about that part of the world and because public discourse about U.S. policy in the Middle East is filled with gaping holes. Similarly, the people who led us into Iraq in 2003 were remarkably ignorant about the history and basic character of Iraqi society (as well as the actual nature of Saddam's regime). To make matters worse, the U.S. military had forgotten many of the lessons of Vietnam and had to try to relearn them all over again, with only partial success.
Second, societies may fail to detect a growing problem if their leaders are too far removed from the source of the trouble.
Third, serious problems may go undetected when a long-term negative trend is masked by large short-term fluctuations.
A fourth source of foolish decisions is the well-known tendency for individuals to act in ways that are in their own selfish interest but not in the interest of the society as a whole.
Fifth, even when a state or society recognizes that it is in trouble, Diamond identifies a number of pathologies that make it harder for them to adapt and survive. Political divisions may make it impossible to take timely action even when everyone realizes that something ought to be done (think gridlock in Congress), and key leaders may be prone to either "groupthink" or various forms of psychological denial. And the bad news here is that no one has ever devised an effective and universally reliable antidote to these problems.
Moreover, if a group's identity is based on certain cherished values or beliefs, it may be hard to abandon them even when survival is at stake. Diamond suggests that the Norse colonies in Greenland may have disappeared because the Norse were unwilling to abandon certain traditional practices and imitate the local Inuits (e.g., by adopting seal hunting via kayaks), and it is easy to think of contemporary analogues to this sort of cultural rigidity. Military organizations often find it hard to abandon familiar doctrines and procedures, and states that are strongly committed to particular territorial objectives often find it nearly impossible to rethink these commitments. Look how long it took the French to leave Algeria, or consider the attachment to Kosovo that is central to Serbian nationalist thinking, and how it led them into a costly (and probably unnecessary) war in 1999.
To sum up (in Diamond's words):
Human societies and smaller groups make disastrous decisions for a whole sequence of reasons: failure to anticipate a problem, failure to perceive it once it has arisen, failure to attempt to solve it after it has been perceived, and failure to succeed in attempts to solve it."