They might want to worship Islam No one worships Islam. Islam is the Arabic for peace and submission - in the religious context, submission and obedience to God. And the Arabic word for God is Allah. Same God as in the Bible, just a different language.
That's maybe a pedantic correction - but I think it's worth making, because there are so many people talking about how Islamic ideas and principles are totally different, and it's just not true. The people who did this were acting in a way that is as much at odds with Islam as the ideas of those White Aryan Christians we read about are at odds with Christianity.
This horrible thing that's happened didn't come out of the fact that people are Muslims - if history had happened differently they could just as easily have been Christians or Jews. It could only happen because the perpetrators saw themselves as being at war, and believed that there are no limits on what is morally permissible in war.
We may indeed think that is an insane way of thinking, but it is hardly strange to us. How can we see it as alien in a culture that has been prepared to wage nuclear war?