Curvy was always cool
And the weightier you were the better. In times when food was scarce or hard to get (i.e. all of human history except the past 100 years), being full figured meant you had, had enough to eat and were a potentially healthy and rich mate. The past century’s emphasis on mass consumption meant that the wealthy needed to stop eating in order to stand out from the rising middle class. Skinnier suddenly became fashionable and has stuck around since as the concerning model of femininity we currently aspire to.