You need height for the blades to catch; like you need height for a ‘chute to full deploy.
Sounds right, and I would think good viz of the ground to get set up. Pilot may have had several things going on all at once.
For auto-rotating to occur, the blades need to come to a stop from turning under power, and set up a reverse rotation in the opposite direction. At 4k feet alt., they prolly never even got stopped before impact, and especially if the faltering engine was inputting any power at all. A chopper that heavy is totally different from a little puddle jumper autogyro. It literally fell like a rock.