One very important point is noted, however oddly enough it is not considered as a main factor and something to think about.
"During the investigation the commission did not succeed to document the method and
level of training of the aircraft crews in formation flying and to document the operating
procedures for flying in formations."
Were those crews qualified to fly in formation at all? Did they have any formation flying training (military or so)?
Flying in close formation is not something that you just brief and do. It takes solid training and solid contracts among the crews to perform formation flight in a safe way.
I am not of the impression that the average civilian pilot is ever exposed to close formation flight, nor does he train it on a regular basis.