The BEA (French AAIB) said it was "very unlikely" that the failure was due to any previous damage.
There was a lot of muddying of the waters after this accident. Initially the pilot was blamed for having performed aerobatics during the accident flight. This was later discounted by eye witnesses, and by the radar trace.
It would suit everyone for the explanation to be pilot error or previous damage, as the alternative is worrying. Since the accident report was published, all DR400's have had their operating category downgraded from U to N, and have to undergo an inspection of the spar.
It has to be kept in proportion, though. One failure, in many hundreds of thousands hours operation - including plenty where the aircraft must have been overloaded or overstessed.