Why??
Thats a good question that I've always asked myself ever since I could start processing properly and logically.
After almost 2-3 decades, my answer is simply "sh!t happens, and for some ****ing cosmic reaons, the stars happened to allign". There is no explaination why and you will drive yourself bonkers trying to ask that question because no one will be there to answer. Regardless of whether you are a good person, go to church every Sunday, live the way of God, or go out every Friday night, shag everything in sight and have 3 illegitimate children, things happen to you.
The only answer that I've worked out is is to learn how to move on from there and apply those lessons in your journey through the rest of your life - that will help with your sanity.
Now where do I send my bill?