OK. I looked and it could be distilled into one word - "stupidity." Flying too close to the walls, not pulling the ripcord in time, fatigue from too many jumps in a day, etc. Also, it has Alpine weather too. Some 15-20K jumps are made a year, so that's a factor...
there is a subset of these dudes that do "proximity" flying instead of just jumping and gliding through the valley. the guy in the video i posted is doing that. "threading the needle" on notches and between trees, etc. they are usually only a few feet from the features they are near and there is no margin for error. potter and his buddy died trying to go through a notch in yosemite.
I'm not familiar with him, but Yosemite is also a glaciated valley, although broader than Lauterbrunnen. I'm not in a position to criticize. I was still doing the really risky stuff kayaking up until I was 50, when I figured out it wasn't fair to my wife and family...
he was almost god-like in the late 80s-early 00s yosemite valley climbing scene
