Gevie,
The questions you ask are normal for any of us who've experienced abuse. Some questions have no answers, some things simply do not make sense. For me one of the toughest questions was "why didn't my parents do anything?" Why didn't someone help me, protect me, save me. I spent years loathing myself, thinking I was somehow flawed because my offender picked me as the subject of his abuse.
A little over a year ago I had a revelation that was monumental in my own healing. I became aware, with absolute clarity, that the abuse was never about me. It was about the sick, twisted mind of my abuser. It was not about anything I did, it was not about the way I looked or acted, it was not about me at all. It was about him fulfilling his own demented fantasies and desires. I happened to be there, I was convenient for him and he preyed on me. He groomed me and brainwashed me simply because he COULD given my own childish innocence.
As for my parents and why they didn't help me or stop the abuse. Again, it was not about me, it was about them. They were too weak to do what was right. For whatever reason, they were so deep in denial that they chose to look the other way. That denial had nothing to do with me.
I believe that this awareness was a turning point for me. In knowing and understanding that abuse never was, nor ever will be about the one being abused, I have been able to release myself of all the questions that have no answers, as well as the self depracating thoughts and feelings.
I hope that in some small way this helps you.