With all of you trying to pontify, may I just point out that the waypoint change occurred 0.81 NM prior to the first waypoint on the Mull. It would appear that the Pilots were unaware - as most contributors still appear to be unaware -that the waypoint entered into the computer was NOT the lighthouse but the Helicopter Landing Site nearby. At this point it was already too late even to conduct an emergency climb to Safety Altitude - but it may have been possible to conduct an emergency climb and just clear the terrain ahead. This they failed to do.