In the "Armoror" article they mentioned that French had covered the area with a meter of topsoil and farmed it. I'm sure after 1944 interesting war ruins containing boots and old duty rosters weren't in short supply and people wanted to get back to normal.
I'm not surprised that the French historians knew about it but didn't see any reason to add to their burden. They have plenty to take care of already. An entrepreneur should do well with this site unless the bureaucracy is in some way threatened. It's pretty new as historical things go so hard to tell.
In Europe there is so much history laying around it's hard to take care of all of it. I lived in Naples, Italy and there are Roman bricks and tiles everywhere and archaeological sites are common. They can't protect or maintain them because there is too much of it.