The Zoom meeting at Jump Crypto was always running. And in May 2021, a scrum of employees was on the screen, discussing a mounting crisis. The Chicago-based financial firm Jump Trading had made its name in the shadowy world of high-frequency trading during the early-2000s “Flash Boys” era, but lately, it had dipped its toes—and then its feet, legs, and torso—into the volatile cryptocurrency sector. The firm had become a kind of silent partner for one of the most high-profile projects in crypto, ...