I was estranged from my father, and he too took it as a surprise that he had 'no idea' about. It was time that I needed... Seperation and growth. Emotionally I was stuck to him and tortured by all the events in our shared past. Appalled even, and he wasn't even so bad. It was all grounded in self-contempt.
Just as a parent shudders when they see their children making the same mistakes as them, I shuddered when I looked at him and saw what I would become.
Though I too had a sort of list that bothered me, I knew that he would never understand a single thing or point of confrontation that I made. You can't condemn someone who is only guilty for doing the best and only way that they know how. This is why he had a similar reaction to you, in a state of disbelief that such a thing could occur. He was completely unable to comprehend.
These sort of things don't just pop up out of nowhere. It's a long, long process that culminates into this estrangement. Ask yourself where it started. Go through the list point by point and really try to see where they were coming from.
If we're thinking in terms of character traits that they despise, try to visualize somebody who, for lack of a better term, disgusts you. You see the entirity of their faults, and see right through their actions into who they truly are. Now picture that you don't like it one bit. Now picture that this person has psychological control over you, is a parental figure or guardian who actually matters. It turns into love-hate.
If we're thinking in terms of specific events, it is the events that just feed into the repulsion as windows to you (or more importantly, them).
This is just my experience, and I'm trying to articulate the feelings that went along with it. Really, I just needed time to psychologically break free from this barrier of self-contempt.
I wonder how anybody could estrange somebody strictly on the grounds that they 'hate them.' If this was the case, they wouldn't need to write an official document declaring their hatred. They would just ignore. Just throwing this out there, but maybe these forms of estrangements are based on self-contempt rather than contempt for the opposite party.
The other forms of estrangement are less psychological, I imagine, and more based on physical events: abuse, etc..