My money is on wind sheer, imo. Showboating pilots, I would hope, is rare. However, if it's Army pilots with Air Force passengers, get ready for a ride. Haha
I've been on Blackhawks and other large military helicopters. I've flown on military contract helicopters, the last being a 4 seater on a high wind day - I guarantee, to this day, my finger impressions are still in the seat frame. I could have turned a piece of coal into a diamond with my butt cheeks that day.
T&P for the pilot, passengers, and their families.