What I believe happened, is an unplanned stoppie. If it wouldn't have had a tire bead holding it together it would have been catastrophic.
So dude is riding along and a unplanned emergency runs in front of him and he grabs a handful of brake, the front one.
Stoppie. Dude is still on the seat as the bike comes crashing down on the back wheel. For a strong highly tensioned wheel, probably not a problem. This wheel ain't that.
So the seam is at a 90° to the point of impact, and dude is not a little guy and his rear is driving the bike down. wheel distorts just enough to bend the pins.
Front rim would just require running into something firmly with the seam at a 90° to the impact.