A Tower Ground Controller reported they observed the Local Controller clear two aircraft for takeoff into the path of pattern traffic resulting in a NMAC.

Narrative

While I was training on Ground Control I observed the Local Controller; clear a PC 12 for departure Runway XX on a 030 heading with a Diamond right crosswind. The PC 12 began turning hard right to their assigned 030 heading prior to the intersection of Runway XY. At the same time; the Diamond was just beginning their downwind turn for Runway XX. From Ground Control I told the Local Controller who was also acting as the CIC (Controller in Charge) to watch that they were going to get close. The Local Controller did not call traffic or take any action to separate the aircraft. When the collision alert activated The Local Controller still did not issue traffic or collision alert. I repeated that they were getting close and he told me he was applying to Tower visual separation. He had his back turned to the window; and I was pointing out the window; saying that the PC12 was bearing to the left to avoid the Diamond; and he still refused to issue traffic and switched the PC12 to Departure.I went back to training my Ground trainee and we taxied Aircraft Z to Runway XZ. I observed that the Local Controller had approved a right downwind for Runway XX for the Diamond. Aircraft Z was released for dept with TMU (Traffic Management Unit) when he was ready. The Local Controller cleared the Diamond to land from the right downwind when he was north of the field; and kept his back; turned to the north. As soon as Aircraft Z called ready the Local Controller cleared them for takeoff from Runway XZ. I was working with my trainee at ground; and before I could say anything to the Local Controller I observed the Diamond making a 90 degree left-hand turn to parallel the departing regional jet. Traffic was never called and instructions to separate aircraft were never issued. I do not believe that the Local Controller even realizes that he had a near mid air. I tried to ask the Local Controller if he was talking to the Diamond and he told me yes he was clear to land. Never once did I observe him looking out the window to scan the area that the Diamond and the departure were in nor did I observe him looking at the radar scope in the Tower. This was pure situational awareness on the Diamonds part to prevent a crash; and their was nothing I could do to fix it. I believe I did everything that I could to not only work my position and train my trainee; but also be a tower team and point things out to the Local Controller. I was the only CPC in the Tower; The Local Controller is a Tower only certified CIC. I do not feel comfortable training and having to oversee newly certified controllers at the same time when they wont listen when things are pointed out to them. There is no room for pride in a safety critical job. My recommendation would be to remind new CIC controllers of the requirement to issue a conflict alert and a traffic alert while also actively separating aircraft; not just being observers. In both of these conflicts; the pilots of the aircraft made evasive maneuvers; and without them this would have been a catastrophe back to back Within a few minutes of each other. Our facility is so short staffed trainees are being pushed through training and as soon as they are eligible for CIC in the Tower they are added to the 6 day work week rotation that the CPCs are doing. There are as many trainees as CPCs. The list of who is not fatigued is shorter than those who are at this point. Everyone is worn out; but that's not an excuse to not issue traffic or a CA (Conflict Alert). The agency can't get us out of the traffic crisis we're in with the way things are currently going. People are so tired they're quitting before they can even get completely certified. I do not have a recommendation for our staffing; but our commitment to safety can not falter. The CPCs are constantly working to fix mistakes of the newly certified Tower Controllers; and this just adds to the workload and fatigue.