I've found myself out of shape in a corner before, coming in too hot with my arsehole cutting button holes in the seat. Regardless of experience level, technique, tires, etc, a moments inattention will undo even the best of riders. Some of the worst roads to ride from a safety perspective are the ones we all seek out...twisty, picturesque, etc...allow your attention to be diverted for a second or two while riding those kinds of roads and even the most experienced among us could end up in the same position. The explanation could be as simple as the fact that the guy was caught up in the moment and allowed his attention to wander to something other than what he was doing...of course that wouldn't make very interesting posts I guess