Autopilot
It seems unlikely to me that experienced pilots would put a fully serviceable aircraft in a 38 degree pitch and roll attitude. The first two things that spring to my mind are AIs and autopilot.
An error in the AIs could lead to the initial confusion, and the standby is not great, which possibly leaves the handling pilot believing he was straight and level when in fact he was nose down. Having recovered from such a dramatic UP at low level it would take any pilot several seconds to gather his thoughts and scan thoroughly away from the standby AI to assess rate of descent.
As with many helicopters the 365 is very lively with the autopilot out. If a pilot takes control with poor visual references expecting the autopilot to be on his side and suddenly realises it is not, then a significant UP will almost certainly occur.
These guys would be used to poor conditions, but with normally minor problems occurring at the wrong time, things were not on their side.
Only a couple of thoughts, there is a long way to go before we know the answers, if we ever do.