The most crucial factor for the failure of ERA in 1970s was the fact that the majority of votes for ratification were not obtained.
Step-by-step explanation:
The ERA ratification was supported by almost everyone. However, a few voices were raised against the ratification stating that the amendment would do away with the protective laws like alimony, sexual assault and would also eliminate the chances of mothers getting the custody of the child after divorce. The needed 38 votes were not received as only 35 votes were received and the ERA failed.