The data show that there is little connection between suicide terrorism and Islamic fundamentalism, or any one of the world’s religions. In fact, the leading instigators of suicide attacks are the Tamil Tigers in Sri Lanka, a Marxist-Leninist group whose members are from Hindu families but who are adamantly opposed to religion. This group committed 76 of the 315 incidents, more suicide attacks than Hamas.
Rather, what nearly all suicide terrorist attacks have in common is a specific secular and strategic goal: to compel modern democracies to withdraw military forces from territory that the terrorists consider to be their homeland. Religion is rarely the root cause, although it is often used as a tool by terrorist organizations in recruiting and in other efforts in service of the broader strategic objective.
Robert A. Pape
Dying to Win: The Strategic Logic of Suicide Terrorism