OK - faulty ATC put 2 aircraft in the same place at the same time.
But the Bashkirian captain clearly had no idea of the correct way to respond to the safety device installed precisely to prevent such an accident happening following ATC cock-ups, even though his co-pilot did. It was the Bashkirian captain's incorrect response to the TCAS RA which killed 71 people.
Sadly the controller, Peter Nielsen, was later murdered by Vitaly Kaloyev, whose wife and two children had been killed in the collision.