They were not asleep, they were deliberately letting the car drive off a cliff because they thought admitting there was a cliff there would make them look weak.
Probably also contributed by the fact that the opposition pointed out that they should avoid the cliff so the only option left is to intentionally drive off it.
Also (to extend this metaphor to all three modes of transport), they were sure that - should any cliff present itself - the greatest nation on Earth will not fall down it, but will boost off and fly towards the sunset.
