The reasons, I think, are explained fairly well in this book. It is not as deeply analytical as I was expecting considering the authors' credentials, but it made several good points that helped me place this attack into a rational framework right away. The first half of the book is about serial killers, most of whom mainly seek power over individuals and many of whom include rape in their attacks. The second half discusses mass-casualty attacks such as happened in Norway. They analyze different types of attacks and different types of motivations. For each point, they give a brief description of a specific case, detailing the perpetrator's background, recent events in his/her life,
motivation(s) and methods.
According to the book, the psychological basis for mass killings is externalization of blame. The killer has not been successful at school, work, or family life, and rather than accept responsibility, he blames outside influences. And yes, it's almost always a "he." The women who have committed mass killings have a similar profile to the men who have done it, e.g., extreme psychological investment in a single aspect of their life, like their career. A lot of them do attack the people with whom they've been in conflict, for example killing their spouse then going to work and then killing the boss and HR officials "responsible" for his job loss.
When they can't blame a specific person for a catastrophic failure, they may blame a group of people. This could be an extension of specific people, such as the entire workplace when only a few "stood in the way" of success, or blame for an entire class of people, defined by race, religion, nationality, etc. One killer attacked Asian children because of xenophobic hatred. The Luby cafeteria massacre was motivated by hatred of all the residents of the town. The person may also decide that society at large is to blame, which makes everyone a potential target for a seemingly "random" murder.
The book didn't include terrorist attacks other than McVeigh's bomb. The next edition will probably pair McVeigh with this guy. The motives and background are similar: military training, externalization of blame focusing on the government, right-wing leanings, and sympathy for a religious cause. They both targeted government buildings and made a point of killing children. The one somewhat unique ingredient in McVeigh's psyche was his belief that he was avenging the deaths of others.
One thing the book doesn't address is why people like this think their murderous rampages will somehow bring about changes they want to see. Even bin Laden's externalization of blame to Westerners had a modicum of logic in his wish that the U.S. would expend its wealth fighting terrorism ... which he believed would reduce the impact of the U.S. in the Middle East. He was wrong, but at least he had a "vision," however twisted.
These mass killers don't seem to think past exacting their revenge on whoever they believe has ruined their lives. They're still irrational, even if they don't qualify for the insanity defense or if they have been able to make and carry out a methodical plan. When has anyone ever decided on a political party or course of action based on the desires of terrorists? I think the IRA may be able to take a little credit for a change in British policy, but only a little.
I can't imagine people in Norway thinking "Wow, I've been so mistaken in voting for the Labour Party. I'm switching to the right wing party right now!" or "Sheesh I've been worshipping Allah all this time when really I should have been a Christian!"
I think where religion enters into these things is that the stories of the Bible give the believers many role models to follow. God didn't target individual homosexuals in Sodom & Gomorrah; he wiped out the entirety of the population to punish them for allowing homosexuals in their midst. He wiped out the whole world with The Flood. He kills the firstborn sons in Egypt. He orders the death penalty for disobedience to one of his hundreds of commandments. This "loving" God seems to really "love" killing.
Religion gives extremists and crazies a framework for their anger and sometimes even helps them define their targets, but the driving force is an inability to accept the difficulties of life. Getting fired for threatening to kill your boss is not the fault of your boss, it's your fault. Getting divorced because you beat up your wife isn't your wife's fault, it's your fault. Not being able to turn your military successes into a successful civilian career isn't probably anyone's fault, except possibly your bad education or your ADHD.
Sometimes shit just happens, or doesn't happen. Some people just don't learn how to get along in society, so they blame society rather than their inability to learn how to behave, or lack of desire to. Or maybe it's because you played video games for hours on end throughout your teen years rather than whip up a little courage to break the ice and meet some kids IRL to hang out with.
Serial killers sometimes have revenge motives too, attacking stand-ins for the girls who rejected them in high school or for their heartless mother. Mass killers are also attacking stand-ins for the people who "wronged" them. You can even include bin Laden and Hitler in this group because they didn't kill the actual perpetrators of whatever wrongs they thought they were avenging.
Where Christianity could actually do some good would be to stop celebrating their unearned forgiveness "through Christ's sacrifice" and teach their kids personal responsibility, accountability, and empathy for others. If more people would be brought up to stop blaming others and look more at their own role in what happens to them in life, there would be fewer murders. Even when unfortunate circumstances really are due to the actions of others, responsibility for coping with it rests with the individual. Just saying "God has his reasons" is a poor substitute for a rational approach to dealing with one's problems.
The Norway attacker didn't die during his attack, so he will be one of the rare ones whose thoughts and feelings can be probed. It will be interesting to see how closely he fits the profile that the peple who have gone before him have established.