She originated a backflip-to-catch release move on the uneven bars, which was the first backwards release ever done by a woman. This and other acrobatics made her a huge star at the 1972 Olympics, and her technical excellence overthrew the sport's emphasis on artistry. She won silver on the uneven bars and gold on balance beam, floor exercise and in the team competition. At the 1974 World Championships, she won two golds and four silvers. She went to her second Olympics in 1976 and won silver on balance beam and gold in the team competition.
But more important than Olga's multiple Olympic medals is the attention she drew to gymnastics. Because of her, girls flocked to join gymnastics and a sport that had previously gone unnoticed was making headlines. She met with President Richard Nixon after the 1972 Olympics, and according to Olga, "he told me that my performance in Munich did more for reducing the political tension during the Cold War between our two countries than the embassies were able to do in five years." (I, uh, don't really know how, or what the logistics of that statement were, but I'll take his word for it.)
I, personally, love it when tiny people do big things and shake things up. But it's definitely not overstating it to say that Olga was a pint-sized revolutionary.