At its peak, the retailer brought in more than $4 billion in annual sales and employed more than 43,000 people worldwide in hundreds of stores. Former employees and industry experts are pointing to the Changs’ insular management style as a significant reason for the collapse.But Forever 21 made its biggest mistakes in real estate. In the years before and after the recession, the company expanded aggressively and decided to open huge flagship stores. The stores became hard to fill with new merchandise, and then turn over, however, and saddled Forever 21 with long leases just as technology was beginning to wreak havoc on American malls.