I've been hiking up there before, I can see how he could've gotten lost. He must've tried going down the ski hut trail, rather than the more traveled summit hut trail. It is much, much steeper than the normal route, a broken ankle could easily happen. Also, it's easy to get lost on your way down because the trail isn't very well defined in areas. It's different than ascending up the mountian, while coming down you don't always have your destination (the peak) in sight and know when you're heading in the right direction, one wrong turn could drop you into a dead end. And because it's so steep coming down, it's tempting to just keep going down hoping you'll find the trail, rather than backtrack and have to climb back up.

I have a friend who used to be in SAR for that area, he said that particular area (especially the neighboring icebox canyon)was one of the busiest spots for rescues. Extremely rugged terrain, very steep, and highly changable weather conditions. Combine that with easy access for beginning hikers and daytrippers, and trouble is inevitable.