they have been in for the last 3 years. Fashion is constanly repeating itself. And since in the last 26 years we haven't created our own style we have to recycle old trends. Leaders and innovators dont exist in millenials, and that is reflected in our art and fashion.
It's a way the fashion industry can make money. A trend hours out of style long enough for a majority to get rid of it. Then it comes back and they realize how much they miss the trend and buy it ll again.