Trump acted as an agent of his father to attack and to destroy his older brother, Fred Jr.
(Mary Trump's father).
Fred Jr. was not at all like his father. He was sensitive and creative. His father wanted him to be a "killer" and to take over his business. Fred tried it for a little while and realized that he couldn't do it. And he chose another career, totally apart from the business and interests of his father.
And that could have been the end of it.
But his younger brother, Donald, wanted the position of heir to the business and to the family. And he decided to help to destroy Fred. Maybe it was just that; maybe he wanted to ensure that Fred didn't change his mind and reclaim his position. Maybe he did it to please his/their father.
Between Fred Sr. and Donald, they emotionally and psychologically destroyed Fred Jr. More or less exiled him from the family. And he turned to alcohol for solace, which inevitably killed him. I'll always maintained that alcohol was the secondary cause of death. The primary cause was Donald and his father.