Our complacency is what caused this.
By "our" I refer to every person who downplays the problem of Islamist terrorism, who are inevitably part of our collective societies. Anyone who uses the word "Islamophobia", who seeks for integration of Islam into civilized societies with Coexist bumper stickers, who compares Islamic terrorism to the Crusades, who calls it a religion of peace, etc...is flat out responsible for the murder of this little girl.
I also refer to the rest of us, who are half sensible, who see the problem of Islamism...but who are yet too impotent to do anything that solves the problem. That includes listening to the former group of people, and even allowing them to have a platform to stand on and speak. If we were actually the responsible guides of society that we must be, then we wouldn't let the former group of people have any power, ever.
Just my view...when you let a murderer into your house, don't be surprised when they kill your family and houseguests. The former group of people has let the murderer in, while the rest of us have sat back and (perhaps complained, but simply) watched.
How do we solve the problem of Islamism? At what point, after this keeps happening time and time again, will we learn?