If you look carefully at the time of original failure, you can see the tail wiggle a few times and the aircraft yaw to the LEFT. Then the TR stops and the fun begins with the classic right yaw. I have a suspicion that the failure was due to loose control cables, which can cause an instability in the tail rotor controls that causes a rapid divergent TR pitch problem that eventually leads to very high left pedal, then failure.
Why not just fly away? There was no antitorque as the right yaw developed, and fly away was simply not possible. This case is far different from the Skycrane, which had merely pulled the rpm low enough to swamp the tail thrust with the main torque.