I've only been a passenger while someone else has ordered (?) an Uber, but my understanding is you say "take me to X location" in the app and then the ride completes when the GPS coordinates of the car roughly match that of the endpoint. Even if doing a multi-part trip (e.g. to drop off multiple people in different places) this is negotiated beforehand and accounted for.

How did this "attack" work, did the driver override the destination somehow?