What is A condition that occurs when a decision making group loses sight of its original goal and a new less important goal emerges is called?

The condition you are referring to is known as "goal displacement." This occurs when a group becomes so focused on achieving a secondary objective that it neglects or loses sight of its original, more important goal. As a result, the group's effectiveness can diminish, leading to less optimal outcomes. This phenomenon is often seen in organizational settings and decision-making groups.