Are you asking about women in the US? If so, I disagree with your premise; major changes came before WWI, as well as after it.

The century before WWI was transformative for American women. For one, the average number of live births by American women fell from 6 to 3 over the 19th century, showing that purposeful family planning was taking place and altering women's roles in and outside the family. In the late 19th and early 20th centuries, increasing numbers of single working and middle class women began living and working on their own, or together, in cities like Chicago, Boston, and New York, where they redefined culture and courtship for decades to come. In the same period, the coverture laws that kept married women from owning their own property or garnering their own wages were slowly repealed.

Female seminaries sprung up from the early republic onward, and higher education institutions offering comparable coursework to men's universities were established from the 1830s onward. At the same time, women began to push for admittance into men's universities, and predominately well off women became pioneers in the professions. Female authors, in particular, asserted themselves in a field that was almost exclusively comprised of independently wealthy men before the 1820s, while other women created the very field of social work. Other women broke into professions long considered taboo for women; Harriet Hosmer, for instance, in the field of sculpture.

Also from early mid-century onwards, women took charge in a number of political movements, and abolitionists and women's acrivists like the Grimke sisters pushed for the normalization of women speaking in front of so called promiscuous crowds (in which both men and women listened to a female lecturer). Closer to the period you are interested in, the progressive movement was in large part driven by female political actors. They were of course key to getting the 19th amendment passed, but women were also key drivers of the 18th amendment, efforts to restrict child labor, end lynching of African Americans, and close down red light districts.

To answer your question more directly, the major changes after WWI were made possible by all the major but lesser known changes that occurred before it.

An incomplete list of sources:

Stephen Mintz and Susan Kellogg, Domestic Revolutions: A Social History of American Family Life

Joanne Meyerwitz, Women Adrift: Independent Wage Earners in Chicago

Beth Bailey, From Front Porch to Back Seat: Courtship in Twentieth-Century America

Patricia Ann Palmieri, In Adamless Eden: The Community of Women Faculty at Wellesley

Mary Kelley, Learning to Stand and Speak: Women, Education, and Public Life in America's Republic

Kate Culkin, Harriette Hosmer, a Cultural Biography

Gerda Lerner, The Grimke Sisters from South Carolina