It is unfortunate he did so much damage to his rig. But I also have to question if he was paying attention.
Any threaded fastener will loosen with vibration or thermal cycling if not locked in one of many ways. My rear turnbuckles are external to the bed. At the end of one of the threaded rods I drilled a small hole and lock the t-buckle by putting a small hitch pin through it. Quick, simple and cheap. I monitor the adjustment as I can see the t-buckle and chain in the side mirrors. Just the slightest slack so I know they are not over tightened.
Off-road is a whole different arrangement. A full rubber mat is a must. I have blocking all the way across the front to transfer loads between the camper floor (not the bulkhead) to the base of the bed's forward bulkhead where it is strongest. That prevents forward movement. I have 2x3's the the length of the bed.This has about 3/4" of lateral clearance and again, this is at the floor, not the lower side walls of the camper. This prevents lateral movement. Up front I have Happi-Jacs, spring-loaded turnbuckles. This holds the front down but has some give. Progressive as the spring resistance increases with travel.
When I leave pavement I will loosen the rear turnbuckles (forged steel, hardware store variety) by about two inches. No more than that so the camper will stay between the 2x3's. To help resist rearward movement I attach quality ratchet straps, horizontally, from the upper turnbuckle mounting eyebolt forward to a secure attachment point at the front top corner of the bed. While preventing reward movement this allows the bed to twist without taking the camper with it.
The essential goal is to allow the truck bed to flex, and it does, without forcing the camper to follow the same flexing which would destroy it. More to the point is that the truck chassis flexes torsionally on the trail. If it, the bed and the camper were all tied firmly together I know the camper framing would follow what the 3/4 ton truck chassis is doing. And it is designed to flex.
On the trail I adjust my side mirrors so I can see both my rear tires and the rear camper tie-downs. It is surprising how much movement there is. This arrangement has worked very well for me on some very rough trails.