Just stupid then.
Immature, and ignorant. Like most his age.
Never had driver education training.
Never had someone teach him how to drive.
Never learned how to handle a vehicle under emergency conditions.
Does not understand the physics of momentum, friction, the roll rate of the vehicle, etc, etc, etc.
It takes time and experience to learn how to 'handle' a vehicle. Many , regardless to age, never learn it. They can 'drive', but they can't control the vehicle during any type of emergency.
Like many young adults and adolescents, he thought driving fast would be cool (and scare the kids) but he exceeded his LIMITATIONS (on driving skills).