What the bombers’ motivations were exactly has yet to be pieced together and may never be fully known. What drives a young man to blow up strangers is most often a volatile cocktail of hormone-saturated ingredients, not always fully transparent to the bomber himself. What is known, however, is that a version of Islam played some role in the Tsarnaev brother’s worldview. This fact is generally regarded as sufficient to count the Boston Marathon bombings as one more grim episode in a long history of religion-related violence. It is common in the secular West to run through a list of such episodes—the Crusades, the Inquisition, Aztec human sacrifices, the European Wars of Religion, the terrorist attacks of Sept. 11 and so on—and conclude that religion has a peculiar tendency to lend itself to violent acts.
Thanks to @fare_fwd for pointing to this article.