Even if Jenny Simpson's shoe had been left on she would have gotten destroyed in the last 800m. She trains more aerobically than most.
All the aerobic mileage in the world can't help you run that 51 second 400m that Kiprop dropped.
It's speed and lots of it that is proving to be the difference maker. Centrowitz found that out in the last 300m when a whole host of athletes blew by him. Tempo runs after a race ain't helping you here, son.