WASHINGTON—The Justice Department argued Monday that a trial judge ignored “fundamental principles of economics and common sense” when he allowed AT&T Inc.’s acquisition of Time Warner Inc., as a host of new details about the antitrust trial became public for the first time.

The government’s arguments came in a brief filed in federal appeals court, where the Justice Department continues to challenge the more than $80 billion cash-and-stock deal—even after the companies completed the transaction in June upon winning a six-week...