It’s a coroner’s hearing, not a trial, and the point is to establish the facts of how the death occurred (accident, homicide, suicide). That’s what coroner’s hearings are for.
It was a coroner’s inquest, not a trial. The jury was a coroner’s jury. Therefore the purpose was to determine the manner of death, sort of a “for the record” thing. Given new evidence from the inquest such as the adults search history and detectable drugging of the children, it is not unreasonable to assume this inquest will have some sort of effect on public policy. Probably not much of an effect but it might inspire people to think about how to prevent this situation from occurring in the future.
The inquiry may also have an effect on people who are thinking about giving their children up for adoption, and people in child welfare services. There are also the members of the public who were deeply concerned, for whatever reason, about the whole incident. Was it an accident? Did we really have such horrible people in our community? An inquiry can put some of their questions to rest.