That's a shocker of a story!.
Over here, trenching below a certain depth,
(6ft, from memory), is a Notifiable Hazard, where OSH has to be notified as to the extent of the trenching.
Our soils over here are way too unpredictable to just start digging and see what happens.
Oddly enough, trench rescue is a skill that that every Fire-fighter here has to learn.
But here is another skill that we are also taught, never let anything come between you and your escape route.
Such a shame to see a guy die, so needlessly.