Aircraft accidents are usually the result of a series of conditions coming together at a tragic point in time. Here we have;
1. Only one Swiss controller at the position, the other had gone to the badroom.
2. The TU-154 handoff was made with the airplane close to the intersection of the 757 flight path, little time for the controller to react to the situation and the crews to respond.
3. The conflict alert system in the Swiss control center was down for maintenance.
4. The phone sytem into the Swiss center was out of order, so the German controllers couldn't alert the Swiss of a potential problem.
5. The TCAS systems on both airplanes worked as they should, but the Russian crew did what the controller instructed by descending instead of climbing, which is the indication their TCAS gave them.
6. Ground controllers do not automatically know when an airplane has a TCAS alert and what type of alert it is (TA, traffic advisory, or RA, resolution alert).
7. The Russian crew was alerted to a possible conflict, but the 757 crew were not.
71 souls lost. It is only a miracle that there were no injuries or fatalities on the ground as in the Lockerbie/Pan Am 747 bombing.