But thanks for that wind chart. I see they got slammed at 3:45 (at the wind meter) winds going up to 40 or 50 mph, with gusts all day up to 30, wow.
So it turns out to be, once again, the ignorance or disregard of meteorological and/or aerological fundamentals.
In all the other sports involved with wind and water (from aviation to sailing), meteorology and aerology are always taught in priority. I don't know about the French schools and their syllabus, but in the area I am, I haven't seen any IKO certified instructors teaching these basics let alone knowing them.
If this unfortunate instructor is to be sued, the schools and kite organisations certifying and employing instructors should be sued first.
PS: the spiral of death is an issue manufacturers should be dealing with; something like fuses (at the kite) which breaks beyond a certain level of strain (or if possible, a certain number of loops).