I only contend that thorough training and a serious approach and understanding of the dangers are important. I don't fly choppers sorry so can't speak of them, but the old drill after takeoff in fixed wing was 'pitch attitude, positive rate of climb, check'. Adequately equipped aircraft can still crash when the basics are ignored. If a pilot is not adequately equipped for a flight I would say that comes under a 'lack of thorough training'.
One accident I remember in particular is the Air Ambo's Kingair out of North QLD on a moonless night. The finding was a clear case of somatogravic illusion. There have been many others and you can find them in the crash comics if you wish.
I realise the original post was about a chopper but this a real danger in fixed wing also.