There is no prime suspect as this is not a criminal investigation. It might turn into one if any evidence shows up. there won’t be.
Calling something a crime scene does not mean a crime has been committed.
The NTSB rules say that if there is a death or fire/sparks involved, they have to treat the area as if it is a crime scene. That means that they need to secure the evidence so it cannot be contaminated. They failed to do that in 2 Cessna engine failures that happened within 50 days and 25 miles of each other, starting 3 days after Fuddy was named in a criminal complaint.
Those are facts. Not opinion, not speculation. Facts.