There are many ways of answering those questions, and each answer we give only makes the mystery darker and more awful. I am going to give you one answer that begins with the very heart of God. For Christians the first definition of God is that God is love. And God was love long before the big bang shot the universe out in space, and long before our world was created with vegetable and animal life and humans in the image of God. God is love, but we all know that anyone who loves gets hurt.
Husbands hurt their wives, and wives hurt their husbands.
Brothers and sisters hurt each other. Parents hurt their children and children hurt their parents. As you know Christians in every church hurt other Christians again and again. So when the eternal Son of God took birth among us on the first Christmas Day he was inevitably going to get hurt. He loved more perfectly than any human being we can imagine.