Actually, that's not just so in what you call the "French legal system" but in all legal systems which are based on Roma law.
The French Bureau of Investigations and Analysis (BEA) concluded in 2004 that the crash was caused by a titanium strip that fell from the Continental Airlines flight and pierced the Concorde's tire.
So, you certainly might criticise that the trial started a) a decade after the fatal accident and b) six years after the the investigations ended.
But to call laws 'crazy' which seek to punish those who are responsible for a the death of 113 people ... well, perhaps you think so because no US-citizen was among them?
But the judges will decide within the four months of the trial who should be held criminally responsible for the crash.