What was one reason why the equal rights amendment failed?

History/details:

The Equal Rights Amendment, formulated as early as 1923 by the National Women's Party, proposed that "equality of rights under the law shall not be abridged by the United States or by any State on account of sex."  Feminist groups in the 1960s and 1970s, such as the National Organization for Women, finally succeeded in getting Congress to pass the amendment as a proposed addition to the US Constitution.  It was passed by Congress and sent to the states for ratification in 1972.  

The National Organization for Women continued to be a leading voice in pushing for ratification for the amendment.  However, conservative groups, especially led by a woman named Phyllis Schlafly, campaigned against ratification.  A key point Schlafly focused on was that women would then be subject to military draft and military combat service in the same way as men. This became the key issue and the Equal Rights Amendment failed to achieve the necessary number of states supporting ratification.