A one-hundred car pileup is not an accident. It is a planned event.
One hundred cars driving fast on icy roads, tailgating each other, guarantees a pileup. If insurance companies didn't pay for damage incurred in pileups, it would result in people driving responsibly. When you get your driver's license, one question asked is how far behind a car must you drive? The answer is one car length for every 10 mph. At 70 mph you should be 70 feet behind the car in front or you will hit it if it stops.
No one does this. Thus a planned wreck, not an accident. If you tailgate you wreck. Period.