It’s possible your mother had some underlying mental health condition. I watched a talk about bipolar and how these individuals can have these destructive outbursts. This can show up in early childhood and they showed these angry outbursts.

It’s possible that your grandmother experienced a lot of denial and confusion.

There were so many unknowns and often parents just did not know what to do. It’s possible your mother always had these meltdowns and her mother just passified her.