I can imagine that nobody wants to prosecute or cover the story because there really is no evidence. People regularly visited a woman who broke her hip and health went downhill in her mid-90's. She clearly stated she wanted to stay at home and did not seem unhappy with her care.
The real story is that she should not have to suffer while ill, especially with so much money in the bank. But prosecutors will assume this is about money and inheritance instead of the neglect in the report.
I am confident that you are right. I just try to see the other sides of a matter. It sounds like you would be happiest to see these vultures found guilty of a crime more so than getting an inheritance. It doesn't seem that you will get that.