Quite simple case afterall. Law is the law, elite athlete sure ain't the law. Kinda shows how Van der Poel is young man, who maybe have lived quite narrow priviledged life, where simple things get sorted straight and quick.
No matter how noisy kids, or adults, athletes don't force the law. In the light of what is told so far, it's completely understandable, that he got fined for attacking civil people.
It looks like his lawyer has him around his finger, milking money from Mathieu. His lawyer should have said 'shame on you, be glad you're getting home already, don't be hothead again' things like that, instead milking him 'we must challenge', (like wtf, kid champion being stupid and you're going to challenge this

)
And. His national team. Team travel management? Zero points.. They should talk with Mathieu a) anger management b) thinking winning formula for the process called 'team travel management' c) this was not the end of the world (happily no worse bruises accidents), think-talk-learn-get better-redo..