This, like any event, comes down to what the family does to keep a case going. There’s many cold cases that are now getting solved by family members rather than police.
There is no agency out there that will keep interest in an issue.
once the media is done with it(they have a super short attention span) and the police will spend all of a few weeks on most things it is the family that keep the interest going. They will pay out of pocket to get attention for it.
There’s even cases where family members that have investigated into commercial air craft incidents because they lost loved ones and helped solve cases on that.
Believe it or not there are people calling the police every day just to keep their attention on a missing person or murder, asking for new leads. These are family members.
Worse: the police DO NOT SOLVE CRIME. Think of all the hundreds of thousands of untested rape kits. Think of all the stories about someone being murdered because the police decided that it was a "civil" matter.