Single engine pilot reported while on final approach another aircraft proceeded to cross the landing runway. The reporter executed a go-around.

Narrative

During an Event hosted by Organization; I was arriving to ZZZ as the lead aircraft of a 2 ship formation. The weather was clear; visibility in excess of 10 miles; minimal cloud cover; and relatively light winds favoring Runway XX. During the approach to ZZZ; I made multiple position/intention calls on CTAF; and communicated directly with other aircraft approaching ZZZ to ensure our arrival would not conflict with others. My pilot-rated right seat passenger was assisting in the visual scan for traffic during this approach; and sterile cockpit procedures were in effect during this time. After performing an overhead break from pattern altitude; we were approaching Runway XX to land; making standard CTAF position calls throughout the approach. While on short final for Runway XX (over the numbers); an unidentified Aircraft Y made a call over CTAF that he was crossing Runway XX/XY. This crossing was to take place at the south end of Runway XX/XY from east to west while departing the event area. I advised that he had 2 aircraft on short final about to touch down (Altitude under 50 ft.); and his reply was that he was 'waved across' by marshallers who were assisting with aircraft parking for the event. Observing that the Aircraft Y had crossed the hold short line; I initiated a go-around and re-entered the downwind for a subsequent landing. The Aircraft Y had barely cleared the runway by the time I passed overhead on the go-around; estimated horizontal distance was less than 100 ft. and estimated vertical distance is under 300 ft. At the time the crossing began; horizontal distance was approximately 2000-2500 ft. My wingman was able to land without incident; as the Aircraft Y had cleared the runway prior to his touchdown. The pilot in command of the Aircraft Y failed to ensure there was no traffic on approach prior to crossing the runway; blindly following the direction of event volunteers who had no authority to direct him to cross a runway.After landing; the large contingent of marshallers (many of whom were in pale 'high vis' vests that were not easy to identify among the crowd) seemed rather incompetent; and I was receiving conflicting information from 3-4 of them regarding the appropriate parking location. There were multiple event attendees walking around in the parking area despite multiple aircraft with engines on at the time. After parking and shutting down; I was informed by an Organization member that the marshallers 'have no full scale experience' and are 'volunteers from a local Club who like to play with airplanes when they can'. He expressed his annoyance at the lack of organization and competence of the volunteers; as well as the frustration at the events that had taken place during my approach and parking. Likely Cause:-Failure of the pilot in command (PIC) of the Aircraft Y to ensure that no aircraft were on approach at the time he elected to cross the runway.Contributing Factors:-Event Fundraiser caused a busier-than-normal condition at an uncontrolled field.-A lack of 'pilot information' provided by the host organization detailing arrival and parking locations/procedures created confusion for arriving aircrews. -Unqualified volunteers marshalling pilots in an inappropriate fashion near a runway; as well as in the vicinity of members of the public in the parking area.-The intersecting runway layout of ZZZ creates potential incursion hotspots; particularly at the southwest corner of the field. Potential Solutions:-Ensuring PICs maintain visual lookout for traffic in and around the airport environment.-Ensuring volunteer marshallers are adequately experienced/trained for the job they're performing.-Compelling organizations hosting similar events to publish information for pilots to minimize confusion when taxiing to/from busy events; particularly at non-towered airports.