I think it might be because he's not a citizen. Otherwise that would be a very strange outcome for a noise complaint. He also could have said something or been dismissive of the police (they were apparently there 5 times?) that made them take things to an extreme.
For something that you aren't fighting the court date is mainly a formality. They read the charge, you plead guilty, pay the fine and are on your way. Given that he has money he probably won't even have to show and will hire a lawyer instead.