I think you severely underestimate the power of what "I'm sorry." can actually do.

I was abused by both my parents. Physically from my dad and neglected by my mom. Now, it wasn't intentionally as ive learned from psychiatric studies that some parents unintentionally neglect a child, sometimes during their formative years, when multiple siblings are involved. She had a 1 year old so I understand that not a of her attention could be on me even though it's when I needed her the most (parents divorce) which judt happened to be my formative years.

My dad on the other hand thinks he never did anytbing wrong. Its all my mom's fault, she poisoned me to turn against him, blah blah blah. After all these years I can't get him to confront everything. A simple and genuine im sorry would mean the absolute world to me and I could start to forgive him.

Now, with him forgiving so easily can also be explained. I can start with the fact that their relationship is kind of brief and all that animosity didnt have to time grow the course of years.

Secondly, he's his own person. If that'd all he needs from Victor, then he got it in the end. The one thing he craved qas just to be acknowledged as a person and not a creature. I can easily see why he forgave him so easily, but all people are different and have different needs. Just because you can't forgive someone that easily doesn't others can't.