What is up with this whole cardio phase of working out just taking over the workout world?

I feel like everywhere I look more and more people, particularly women are moving towards a more cardio focused workout. More and more people are running half marathons or full ones. Cycling classes are the new craze and lifting weights and gaining muscle is a thing of the pass. I really wonder if the gymfluencers have started this trend amongst women. I did not want to belive it until every single one of my girl friends and girl cousins started to same type of workout routine. Is doing cardio the new wave of working out? I hope so because the gyms just seem to stay packed.