In fast fashion, there’s something known as the “impossible triangle.” It’s the perfect production scenario, where a company can 1) quickly onboard lots of new styles at 2) low prices, while 3) being hyper-efficient in managing massive volumes of inventory. Unlike Shein, those other upstarts didn’t quite crack the third edge of that triangle. And that’s what left them trailing — according to Crunchbase — the fourth most-valuable tech startup in the world, with an estimated $100 billion valuation.