I spoke to someone the other day about this, him having zero knowledge of the railways, his response about the driver hitting his head was, "do they not have seatbelts?" to which I flippantly replied, "no, they don't have airbags either!", I doubt even with that, the poor guy would have survived the impact, also neither would travelling in a Pendo or many other stock, the other people you could argue, may have survived.
In terms of the controllers, what do they have to go on? how would they know how bad it was at the crash site other than what they have been told by other drivers, they knew the landslip at Laurencekirk was bad but as stated previously, other trains had gone past the crash site with no issue, the affected service had been through some time before and had the driver seen something, would have obviously reported it, I haven't had time to properly look but how long before the HST was turned back was it that another service had gone along that same bit of track?