My [15F] family still thinks my dad [38M] overreacted when mom [37F] hit me because he divorced her.

There's layers to this whole situation. I had a sister who died at 9 years old from cancer when I was 11.
One day when I got home from school I wanted to go into her room to put the new flowers in her vase that she always liked. My dad even said it was OK and bought them for me. I accidentally knocked the vase over and it broke. It was a complete accident and I felt awful. My dad was on his phone talking to a client when he heard all the commotion with my mom going on upstairs. She had come in and was yelling in my face shaking me. She hit me in my face with a closed fist. My dad walked in right as she hit me. He pulled her away and was yelling at mom. He got right in her face angrier than I had ever seen him before.
Dad kicked her out of the house and he won the divorce. Mainly because he knows some really good blood in the water type lawyers. He has sole custody of me and I haven't seen my mom in 2 years now.
My family still has this idea that dad overreacted, and it's caused massive tension between dad and his parents. They believe he's going to start doing what he did when he was a teenager and sleep around. I know my dad is seeing a woman who's name is Peyton but I've never met her. It's just caused a lot of tension because they still think he overreacted by divorcing mom.

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tl;dr: My dad divorced mum because she hit me years ago because of an accident. My dads family has always thought he had overreacted to the situation. How can I get them to stop feeling this way about dad?


Source.