The Crime Syndicate imprisoned the Justice Leagues inside the Firestorm Matrix which psychologically placed them in situations that depicted their greatest failures. Wonder Woman was placed in a situation where she was forced to do battle against both Amazons and humans for the lives of Superman and Steve Trevor. Martian Manhunter and Stargirl attempted to break her out but Wonder Woman ignored them.
Following the Rebirth retcon, the "Year One" storyline explains that while put in a cell after coming to Man's World, Diana was visited by the Greek gods in animal form. Each gave her powers that would reveal themselves when she needed them to. She first displays strength when she accidentally rips the bars off her cell door when visited by Steve Trevor, Etta Candy, and Barbara Ann Minerva. Later on a trip to the mall, she discovers super speed, great durability, and the power of flight while fighting off a terrorist attack.
I thought George's one "mistake" in rebooting Wonder Woman was making her only 25 years old when she left Paradise Island. I preferred the idea of a Diana who was thousands of years old (as, if I recall correctly, she was in the TV series). From that angle, I would have liked to have seen Diana having been Wonder Woman in WW2, and be returning to our world in the reboot. Not having that option, I took the next best course, and had Hippolyta fill that role.
^ Greenberger p. 175: "Journalist and feminist Gloria Steinem...was tapped in 1970 to write the introduction to Wonder Woman, a hardcover collection of older stories. Steinem later went on to edit Ms. Magazine, with the first issue published in 1972, featuring the Amazon Princess on its cover. In both publications, the heroine's powerless condition during the 1970s was pilloried. A feminist backlash began to grow, demanding that Wonder Woman regain the powers and costume that put her on a par with the Man of Steel."