Ever since the two alleged perpetrators of the Boston Marathon bombings were identified as Chechens living in America, the constant refrain in the media—as is almost always the case after terrorist attacks—has been to ask "why?" Apparently, many media pundits simply cannot comprehend how seemingly normal and relatively successful individuals could be motivated to carry out such actions.

Clearly, they have been misled into believing that one must be poor and disenfranchised or mentally disturbed to carry out acts of terrorism, despite a wealth of empirical evidence indicating that terrorists tend to be relatively well-educated, from higher socio-economic strata, and do not exhibit disproportionate levels of psychopathology. Still, the default assumption — at least in cases of jihadist terrorism — is that personal grievances of some sort must always somehow be responsible. That is true by definition for individuals who carry out acts of violence for idiosyncratic personal motives, but it misses the point entirely when one is dealing with ideological extremists.

It is the adoption of extremist political and religious ideologies that is the primary causal factor in precipitating acts of non-state terrorism. And it should be self-evident that those who formulate or adopt extremist ideologies must necessarily be disgruntled and alienated from the current social or political status quo, whether justifiably or not. Why? Because people who are happy or essentially satisfied with the status quo are neither going to create nor embrace radical worldviews that advocate attacking the existing system in order to establish what they believe will be a better, more just world.

Thus there is no mystery at all about why the alleged Boston bombers committed their terrorist atrocity: like the perpetrators of the 9/11 attacks and thousands of other jihadist terrorist attacks throughout the world, they had embraced a radical Islamist ideology that enjoined them to wage armed jihad against the "infidel" enemies of Islam. It hardly matters why the Tsarnaev brothers became disgruntled or angry—people can become disgruntled and angry for a vast array of both legitimate and delusional reasons. What matters is that this underlying emotional attitude made them receptive to and ultimately caused them to embrace Islamist doctrines, which offered them an explicit, coherent, and theologically sanctioned justification for perpetrating violence.

Yet that undeniable fact is consistently denied in cases of jihadist terrorism, both in the media and even by government officials. Perhaps the most egregious illustrative example is the case of Army Maj. Nidal Malik Hasan, whose jihadist terrorism at Fort Hood was foolishly ascribed to personal grievances in the U.S. military's own investigative report. However, the evidence clearly indicates that Hasan had increasingly embraced radical Islamist doctrines, and that in the months before his attack he had extensive email contact with Anwar al-Awlaqi, the al Qaeda operative who was linked to numerous jihadist plots, became a key figure in al Qaeda's affiliate in the Arabian peninsula after leaving the United States, helped prepare the group's English-language magazine Inspire, and was killed in a drone strike in 2011.

Here one can observe a blatant double standard at work, since Islamist ideology, uniquely amongst extremist ideologies, is rarely if ever identified—much less highlighted—as the primary motivational factor behind terrorism committed by certain Muslims, even those who proudly proclaim their adherence to that ideology. In contrast, the media have no qualms about rightly emphasizing the role of white supremacist ideologies in precipitating acts of violence or terrorism by neo-Nazis, Klansmen, and certain right-wing militiamen; the impact of extremist interpretations of Christianity in fomenting anti-abortion violence; or the degree to which apocalyptic millennarian doctrines have generated violence by groups like Aum Shinrikyo. Nor do the media customarily refrain from noting the communist ideological agendas of left-wing terrorists, or the underlying beliefs fueling the violent actions of certain eco-radicals. Why, then, is the role of Islamist ideology so often downplayed or denied in connection with acts of jihadist terrorism?

Those who are now claiming that the Boston bombers' actions had nothing to do with their adoption of particular interpretations of Islam are seriously mistaken. And those who are foolishly endeavoring to portray the two Chechen Muslims as the innocent victims of covert manipulation or anti-Muslim prejudice—rather than as brutal victimizers—are either being disingenuous or living in a state of psychological denial, if not in a parallel mental universe.

The main substantive questions still to be answered in the Boston Marathon bombing case are whether the two bombers were part of a larger local cell or had received any tangible logistical or operational assistance from an organized jihadist group or network abroad. But it is all too obvious why they committed the reprehensible acts of terrorism.

Jeffrey M. Bale is an Associate Professor and Senior Researcher in the Monterey Terrorism Research and Education Program at the Monterey Institute of International Studies