There is always the opposite question to of why do good things happen to bad people
But yeah.. it is a corrupt world. Jesus does though in the end restore it all to glory.
Suffering and pain and evil is horrific to be part of and see. The experience of it is at a level where people lose sight of God.
Jesus is right there in the suffering though.. feeling it with who is going thru it.
Why doesn't he stop it? Well he will in the end. And He is just.. the evil doers get their comeuppance.
A Muslim man who gets the girls head cut off?
He's cut off from a place in heaven, unless He receives Christ as His Saviour.
So he would have a place in hell unless saved.
So the justice? The girl is dead but probably in heaven due to her age. The man is headed for hell.