Last Wednesday, a car lay upside down below a parking garage at the Shanghai headquarters of electric vehicle firm Nio. Shards of glass encircled the vehicle, as did a crowd of stunned onlookers that had just witnessed the Nio car plunge three stories from the parking structure above to the pavement below. The crash killed one passenger and a driver, and so far little is known about how and why the car punched through the third-floor wall to its deadly descent. The company claimed that the accident was “not caused by an issue with the vehicle.” Social media users called...