The heli was over 15 years old. The chances of it having a sudden mechanical failure is pretty high.
Helis do not always auto-rotate. All it takes is for one blade to come loose or the whole engine could've jammed up. There are all kinds of shit that can happen.
My bud has LOTS of stories. Including the time they had a failure in their marine helicopter , but luckily was able to auto-rotate to a very stiff landing. He counted himself lucky. He said there were ALWAYS oil leaks and this and that to watch out for.
He wouldn't fly on one now.
There have been crashes of heli in the Grand Canyon and Las Vegas and Hawaii.
These things happen.
I don't think prima facie , it was anything other then an accident. We don't have James Bond type super-villains I don't think.