I think it is probably straightforward for a trained professional to document the circumstances of a person's death. I suspect it is a lot harder to conclusively say "but for X, they would have survived". widespread fraud by coroners does not seem likely, but apathy and prioritization of resources is believable.

I believe that some people will do things surprising to me when it means money for them or their organization.

A recent case in point are the people in charge of the Harvard medical School cadavers who sold the organs on the sly, but you could probably find other examples of cases where monetary incentives distort what we were consider commonplace values