I'm not aware of any aircraft that would lose rad alt, landing lights, etc etc in the event of a double engine failure. There is a battery on board, and most ancillaries are driven from the main rotor gearbox, so whilst the engines or rotors turn the gearbox and the battery is switched on, then you should have all you need for an emergency/forced landing.
It seems the rotors/main gearbox were not turning. Images of the blade tips indicate this and the AAIB report confirms the fact. Astonishing information.
It seems the engines were not running - but perhaps could have been given the amount of fuel recovered. Coupled with the above, astonishing also.
Without a doubt the most curious of combinations.