The pilot reported that he was preparing for a display flight in a local airshow which included a preflight procedure to rotate the engine prior to start for lubrication purposes. During the procedure, the electric starter motor struggled to rotate the engine due to viscous oil because of cooler overnight temperatures, and the main circuit breaker had tripped. The pilot turned off all cockpit switches, but forgot to turn off the magneto switch, and exited the airplane. The pilot then utilized a hand crank to rotate the engine, and the engine unexpectedly started. The wheel chocks had been previously removed in preparation for the planned flight, and the airplane began to move. Several ground personnel attempted to stop the airplane but were unsuccessful before the airplane impacted two parked airplanes. The airplane sustained substantial damage to both wings and the elevator. The pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation.