Step mother exploiting my dads assets, for 30 years. She would tell us, we would tell dad. Why did she tell us?

When they got married when alone with her she would tell my brother and I she did not love him but loved his money and she deserved it, we told Dad but he did not believe us. They have married about 30 years now and he is 94 and she is 78. she told us that dad would not do a will leaving her everything and mocking him, would tell us because he loves his sons and she was mad. She would say it in front of him. She would ask us to help her convince him he needs a will. Then while in California my brother went to visit him he had scratches on his face, her ring when she slapped him cut his face. We could never get him to leave her its like he had no will of his own. Then one incident Her sister called my brother and feared for our Dad's life and said our step-mother told her she was going to kill him for his life insurance. My brother confronted her and she denied it, but on same hand never talked to her sister again. She told me as soon as he was unable to work she was going to leave him. HE worked freelance estimator and made 150,000 a year in California. He worked till he was 85. She left him and went back to Kansas talking all but a few thousand of his assets. The step-family jumped her and she took him back which was a mistake on my brother part because he took him to her. We should have got dad help instead She told me when he was no longer able to take care of himself she was going to put him in a nursing home. I called him and promised him, if she tried putting him in a home I would come get him and take care of him. In 2010 he ended up in the hospital she told me she was not going to bring him home but was going to put him in a nursing home. So I went to see him with a video recorder and showed it to him, Because I live in a different state and had limited funds to travel back and forth I told him this was probably going to be the last time I can come down. I told him he was going to go to a nursing home the next day and I offered to take home and take care of him just like I promised I would do. He said he did not want to go to the home but he did not want to make her mad, so he declined my offer and I did not press him. Later I asked her to save her money if she would just let me take Dad home and she told me that he could not live without her. She wanted me to ride in the ambulance with him to the nursing home and I would not. she found out the cost and took him back home by the next month. My brother had stayed several months the summer before bringing him back to her and he told me that she wanted him to take care of dad to free her up so he did. He said she would go crinkle up the throw rug and tell him leave it that way and maybe your dad will fall break his neck and die. But he told her if he didn't you get a big hospital bill, and she said ok maybe you better straighten it out then. She would crank the air thermostat on a hot day up to 80 degrees. My brother would turn it down. She would get mad and demand money from my brother to help pay the electric. All total he spent about 3,000 dollars to take care of my dad in a 785.00 month apartment for 3 months. He could not take it any longer and moved out. My brother said his personal papers and the family bible given him by mom and dad was gone from his belongings.
She gave his car to her son at his objection in front of him. Took his social security check from his fingers at his objection when he checked the mail before she did. She had since hired an attorney late in 2011 had him declared incompetent and got guardianship we tried to fight her but she had all the resources and we had none. Her attorney band us from seeing our dad. WE only know he is a live because it has not been published he has died. We reported her for abuse but she would turn it around on us make us to look like we were gold diggers. So I was thinking seeing a forensic physiologist who does hypnoses and who has worked and testified in the courts to interview my brother and I under hypnoses to prove our love for our dad and stop her from getting away with everything she has. The state this is happening in does have court cases in which forensic physiologist who do hypnoses were used in court. But the problem I'm having is why did she continue to tell us what she was going to do? how she felt about him? She knew it had to be hurting us.
I don't understand? I don't think she got her way until he got to frail and isolated. I have read the victim will say he can not live with out her. But can not find where the abuser says the victim can not live without her. That is the opposite. I have read where the victim will be afraid of making her mad, even more afraid of that than going into a nursing home. I fully expected my dad to take my offer. He was a contractor and hated walking in nursing homes. He hated the smell. But yet he chose the nursing home over making her mad. I have a lot of questions the greatest one is why tell us she going to hurt our dad?