Some of the details above are wrong. For example, while Gimli did have a go-kart league, that was not the group using the runways that day. It was a car racing group. The races were over for the day, but they were having a cookout at the end of the runway. If the plane hadn't stopped in time (and there was doubt it would be able to) they would have plowed right into all the campers and trucks parked at the end of the runway.
If you're wondering "how did they run out of fuel?" it was a combination of like five things. The big ones were:
*Greater automation meant that there wasn't a flight engineer, and nobody had written out what of the flight engineers jobs needed to be kept and given to the pilot and copilot and which were simply unnecessary
*One of the computer chips monitoring the fuel level had malfunctioned and not been replaced
*Air Canada was in the middle of a transition period where some planes were using metric and some were using imperial, and there was confusion in the calculations for how much fuel they needed.