"Wait, he's suing the city because he thinks his crash is city's fault for lack of maintenance, despite it literally being illegal to ride a scooter there, and, on top of that, being too drunk to drive?"

I assume he suing because he has nothing to lose but a lot to gain. The lawyers likely took it on gamble (contingency). He has a chance of settling since the risk and cost of litigation is huge. If he loses, there's no way he's paying any counterclaims for legal fees. So it's sort of like, why not? (Not that I think it's right)