Lots of suppositions and assumptions looking for someone to blame while the truth is most probably much more simple :
Try this : An agent that want to please and impress his client ( I can get you a private aircraft to get to Cardiff, forget commercial via or CDG or AMS ) , a young guy that is impressed by it , (and frankly would anyone refuse this ? ) A friend that know a friend that has a Malibu and can do this cheaply ( or even for free ) a Malibu ? for 99% of people a Malibu is a very sleek turbine private a/c , who had heard of a piston Malibu before ? The owner of the aircraft calling one of his friends always eager to fly , saying , Mr X ( who normally flies the plane ) cannot today you want to fly to Nantes and back with it to get someone important ? Who will say no ?
You arrive there , the weather is not to your liking but the kid and his agent are pushing to get there as he has first training with this new club and full media coverage the next morning . So he is pushed in a corner he does not like but not in a position to really say no .
During the flight something happens not planned that he did not encounter before , electric, icing , engine , whatever, everything gets aligned , and bingo!.
Really nothing much to do with N- registration or Commercial or EU legislation . Everyone of us could have been caught in this . and the more I think about it , me included . The only thing that differentiate us all in this situation is our power to say no. The rest is just bar discussions with Mr hindsight.