How Shein and Temu, which are spending billions on digital ads and offering steep discounts or free products, have become big threats to Amazon in the US (Louise Matsakis/Big Technology)

Louise Matsakis / Big Technology:
How Shein and Temu, which are spending billions on digital ads and offering steep discounts or free products, have become big threats to Amazon in the US  —  In the fall of 2020, Amazon looked unstoppable.  The pandemic lockdowns had supercharged its e-commerce business …