The cancellation of the most-watched show in late night TV, Colbert’s Late Show, stunned the TV world Thursday, as well as CBS staff.

CBS, citing economic issues, announced that his program would go off the air next May, news that came at a time when its corporate parent, Paramount, needs the government’s approval for a merger with...

Executives at the network said in a joint statement that the decision was “not related in any way to the show’s performance, content or other matters happening at Paramount.”