Watch and Learn: Double Bike Crash in the Same Turn [Video]
The two riders were most likely under the spell of the twisting road under the forest canopy and laid to heavy a hand on the throttle of their machines, but their journey ended in pain. Just as may other roads in the forest, the asphalt can become very slippery with dead leaves, dirt and gravel, so blind turns are better entered at a safe speed.
Regardless of how good a rider is on clean tarmac, reaching a dirt patch in a turn while leaning hard equals a spill in 99% of the cases, with most riders crashing after encountering pebbles or even a wet spot.
Too bad to hear the front rider (who by the way was a girl) suffered from pelvis fractures in several places, but things could have been so much worse in case she came off her bike right in front of the incoming car...