I can't explain or justify the behavior of those who abused us. I know two former perpetrators and the response I've received from both is that they acted out of an overwhelming need. I'd call it an addiction (many may disagree), but the urge was so compelling they felt powerless to resist.
If that's correct, they struggle with greater internal monsters than we do. Generally, perpetrators are victim-survivors of sexual abuse and carry the pain most of us have experienced. On top of that, they also become victimizers.
I believe our abusers are tormented by their actions. Even though they feel they can't help themselves and find excuses for what they did, they also know they did something terrible. They stole our childhood innocence and brought immeasurable pain into our lives. Consequently, I see them as people in even greater pain than the rest of us.
It took me years to feel that way, but now I've learned compassion toward myself but also toward the abusers. I had to move beyond my own pain before I could understand that those who hurt me were also living in agony.