Sometimes the secret to get out of trouble and carry out the mission, one must play the dumb card. In certain cases, to be perceived as sharp makes people go up in arms. To speak your mind only hurts feelings. To play dumb prevents confrontations, judgements, and friction. It protects the boss’ ego when a psychological safety net is not provided. It makes the team members like you better. When everyone gets along, the mission is carried out. I guess that is what tact sometimes means in practice.