CFT, especially with helicopters, is the main cause of course.
https://www.dailymotion.com/video/x5sx8qp
This also happens in fog, helicopters are just dangerous.
There is a saying and it goes something like this... There are old pilots and there are bold pilots, but there are no old bold pilots. It is not actually true because a lot of us have gotten away with stuff that should/could have killed us.
My wife and I live on a small airport. A few years ago, a very experienced friend of ours flew the airplane he was flying back from an airshow into the side of a steep hill in an area that he was very familiar with. This was someone who flew VFR (visual flight rules) in low visibility conditions many times, and it finally caught up with him.
We started out hang gliding, joined an ultralight airplane club which evolved into an experimental airplane club and finally a vintage airplane club. We knew this guy from when we were all into ultralight aircraft. The airplane he killed himself in was a high performance homebuilt experimental. He was the one flying, the guy who built it had less experience and was in the right seat. My wife and I had both flown with him previously and he took a lot of chances. We never flew with him after we got our own General Aviation aircraft.