The bench is not even close to the technical nature of the snatch. Anyone can learn to bench in 10 minutes...the snatch takes a lot more coordination and athletic skill to do properly. I used to snatch quite a bit and almost got to my bodyweight. Throwing 140+ lbs into the air in less than 1s and over your head requires more power than bench.
Anyway, I'm pretty sure Stafon was using the (moronic) thumbless grip on the bench. I've seen people drop it like this onto their chest. I've never seen anyone drop it wholeheartedly onto their chest with a thumb grip. It only requires a little bit of sweat or lateral motion to have the bar slip. Even when going for reps I've never seen the bar just totally collapse. The athlete is always exerting a force, even if it's just a little, to have it not just fall down. No spotter could spot 280# if the bar fell. No spotter. None. The spotter did, however, let them either (1) use a thumbless grip (2) let them go too far past their max.
The S&C for SC needs to be fired, imo, if he didn't (re-)teach them proper technique for the bench. The bar should only be above your head/neck for .1s while you move it from the rack (which should be BEHIND your head). Anyone that benches with their head under the rack is asking for problems. Let the bar fall on your chest and never put it in a position where it could fall on your neck. Proper technique should always be emphasized, even if you have to go down in weight. I know when you have guys bench the testosterone is high, but serious weight can cause serious, life-threatening injuries. That's why when I saw our lifting videos I cringed. We have serious technique issues on the clean and squats (which destroy the knee).
About a dozen to a half-dozen people DIE every year from the bench press because of this. Hopefully everyone will try and learn why it happens and how to avoid it now.