People seem to be confused here about what happened in the race. I heard the US channel commentators didn't pick up on obvious things, on CBC (Canadian) it was very clear.
Earlier in the event was an incident where the organizers rang the bell one lap too early, causing the leader of the 3000m steeple M to sprint like it's the last lap and then jog the true last lap, getting passed by many runners instead of contesting the win.
As a result, the female 3000m steeple runners were instructed to keep track of the laps themselves and not trust the bell ringer to avoid a similar situation.
Kiyeng counted the laps herself, and miscounted them, thinking the penultimate lap was already the last one. It was obvious that she surged and used all her energy on that lap, she was also creating a significant gap. After the penultimate lap she realized she still has to do one more and slowed down considerably. Coburn was easily making up the distance. She knew exactly what happened (Kiyeng miscounting and kicking too early) and was already excited to win the race. That caused her to lose focus and trip on the water jump. This had nothing to do with lack of fitness or chasing an unrealistic time, it was just the excitement of knowing she is about to win Monaco because the runner in front of her had nothing left.
Lesson learned, the real question is who would win if neither of these events happen (Kiyeng miscounting and Coburn tripping), currently it seems to be in favor of Kiyeng.