That comic, DCU Decisions #3 2008 is set during Wonder Woman Vol 3 #22 (or so) As a result of the Amazons Attack story line, set around Wonder Woman Vol 3. #16 (or so):
Athena appears, displeased with what the Amazons have done and prepared to pass judgment. Circe is banished to Hades. Themyscira rises from the ocean. The Amazons disappear to parts unknown. Hippolyta is exiled to rule over an empty Themyscira.
Athena watches events unfold, with the Greek gods in chains behind her. She reveals that the Amazons have been turned into regular mortal women scattered throughout the world with no memory of their past lives.
Due to behind the scenes manipulation, Themyscira has been depopulated, while Diana and Donna still around in the U.S. This gets resolved a few arcs later, involving Darkseid.
This series ended with the New 52 reboot, and everything changed.