Jason Bright, Tim Blanchard, Lee Holdsworth and Kelly's trips off the track all brought yellow flags, while Alex Rullo also failed to finish. At the front, the Falcons of Coulthard and McLaughlin steered clear of the drama.
"I didn't think it was possible after qualifying," Coulthard said, who started from sixth. "It's been a great day - I think we should leave here pretty rapt.
"One-two for the team, it doesn't get much better."
Polesitter Jamie Whincup was edged out to third, with Craig Lowndes fourth. Coulthard is denied the overall series lead, due to a 35-point deduction for his role in the Saturday crash.
His bump of Rick Kelly was the first action in a concertina-style crash that drew in 12 cars, and ruled out Will Davison, James Courtney, Taz Douglas and Rick Kelly from Sunday's race.
The 34-year-old responded in style in the 200km classic, holding his nerve through dicey racing conditions to claim his first regular-series win for his new team.
Van Gisbergen leads Coulthard in the championship standings by 20 points, with Whincup third and McLaughlin fourth.
Mostert, who finished seventh, was left to rue his late-race misfortune.
"I lost a victory for the boys and I'm pretty gutted," he said. "The boys did everything right today.
"One little lock, touch a little bit of water and you fall off the back of the curb."