Flight Instructor in the pattern at a non-towered airport reported they observing a NMAC between two other aircraft turning onto the final approach course at the same point.

Narrative

Aircraft Z; made a non-standard entry into the traffic pattern for Runway 26 at VAY. Ahead of Aircraft Z in the pattern was Aircraft Y. Aircraft Y started their base to final turn and they were number 1; they made a radio call indicating their turn to final. Shortly after Aircraft Z announced he was turning base to final with seemingly no awareness that Aircraft Y was already on final. I was watching it unfold on ADSB-in from my plane; Aircraft X. The aircraft appeared at same position and same altitude on ADSB-in. While on final Aircraft Y again made a radio call stating intentions. Aircraft Z seemed to finally become aware that another airplane might be on final as well and asked what airport the final traffic was at after another aircraft in the pattern; I forget the tail number and type; called out that there were 2 planes on final; Aircraft Z stated that they would land and get off the runway as soon as possible which led them to descend below Aircraft Y. Aircraft Y executed a go around to avoid landing on top on Aircraft Z. From my perspective Aircraft Y did nothing wrong and all of their actions were safe and compliant with FAA guidelines. Aircraft Z was the aircraft causing the near mid-air collision due to non standard behavior and lack of situational awareness.