500 miles is the scheduled distance, but there’s a rule in place where they’ll extend the length to try and avoid finishing under caution conditions.

The drivers usually lose multiple pounds in sweat per race. Ain’t no antiperspirant that can handle that (I know you were joking)

It used to be a LOT easier to end under caution than it is now. The rules have changed multiple times to give them the most opportunities to end under green. But here’s the reason why a caution on the last lap ending it makes sense: during last year’s All-Star Race they did away with it and experimented with being able to line them back up no matter how last second the wreck was. Ryan Blaney was literally ten yards from the checkered flag when the caution came out. He crossed the line literally less than a second after the caution waved, and (understandably) had no clue it even happened and thought he won. He unfastened his window net to celebrate and prepare to exit the car…only to be told he had to restart again. So now you’ve got a car with an undone safety device who has to race more.

Would that exact situation happen every time? Probably not. But you can see how last last moment cautions lead to clusterfucks. There’s gotta be a cutoff somewhere and the last lap is a pretty generous place to put it.

It’s not about ties. A caution flag in NASCAR takes up about 5 laps for them idling around the track while the incident is cleaned up. If this happens with like, 2 laps to go, they won’t just have the race reach its scheduled distance and end with the field under caution. They’ll extend the length of the race so there can be a green-white-checkered: a 2-lap restart where the field takes the green flag, goes around to take the white flag, and then comes to the checkered flag. If another wreck happens before the white flag is reached, they’ll try again. This can lead to the race distance being extended multiple times.

In this case they had reached the white flag at the time of the final crash, and because of this the race was ended as soon as the caution flag flew. Stenhouse was the leader at that point, and was therefore declared the victor.

I really hope that was at all concise! I work within racing so I’m happy to answer any other questions.

It’s actually happened a good handful of times, this wasn’t some super unprecedented outcome. This year was just the longest.