If I had to choose three, I would say

  1. The dominant discourse was that women didnt care about looks, they cared about personality, men cared about looks because they are shallow. Now we see women openly admiting that looks are the most if not only important factor for hookups

  2. There was a traditional idea embraced by feminism in some ways that women are naturally modest and men are the ones that are dirty pigs that only think about sex, women dont like to be sexualized and objectified. All the twerking and the normalization of Onlyfans and the push for more and more revealing clothes proved this one wrong, and the discourse shifted from "men want to see us naked on every magazine and outdoor, thats disgusting! We women dont want to be viewed as an object" to "If women do the exact same thing (this objectification) but 'on their terms' its not only good and natural but empowering" (also part of this one is the "women like to make sweet love, men like to just fuck" that research about female preference in violent porn and in rough sex disproves time and time again)

  3. There was the idea of the long term game for men: be a good man, work hard, and you will get a good wife. Lots of men realized it wasnt worth it if other men were having success in the short term game with the same women they would end up marrying with in the long game. They either started focusing on hooking up or opted out