The incident causes a lot of turbulence on the German forums*. There is some argument about the signposts on the beach: while all agree there are some, they are described very differently ("Lorry-size" is mentioned by one); some also state there are traffic lights - if so, I presume the radio operator can activate them as seen appropriate. But there is never an answer to remarks regarding the nature of the runway - shortish, and water at both ends with only a tiny bit of beach between) which might well inspire a pilot to come in lower than usual. The slightest bit of downdraft is then sufficient to provoke a mishap.
For myself I can't understand the aerodrome operator does not control the active runway's short finals area more intensively. A 4x4 in emergency services' colors a few times per hour should do the job, except for those really persisting in their stupidity (and for those, no help is possible anyway).
Certainly the operator has every motivation: if ever things come to grief, as they must do one day if things go on like this, the blame will be mostly if not exclusively on them.
*for one example, those who read German may look at
https://www.pilotundflugzeug.de/foru...,02,05,2017507