I think that there may be a mistake in the report. I think the engine must have died before crossing the line. Dumas must have kept the car going in order to actually get across the line, as if the car stopped before the line they would not have been able to push it across. (the rules state that the car must cross the line using it's own power).

Here is what Lieb had to say about it:

Marc Lieb: "Our target was it for sure to let the time pass by. But while slowing down the engine broke and couldn't get started again. Maybe that does sound completely insane but it's just what it is."