The Chevelle rear ends the Audi, then there's some side contact, then after the tunnel there's some heavy contact with something we don't really see. The impact from the rear ending would've been minimal since the closing speed wasn't great. And being a modern car, the Audi would have side impact protection. The only thing that seemed off was when the Audi tries to T-bone the Chevelle. With crumple zones at the front of modern cars it would've looked wrecked, even if the contact was at a relatively low speed.
here is little Effie's head
whose brains are made of gingerbread

Later after the police got involved, the Chevelle got into other crashes but initially, they were only banging into each other.

Pretty sure the Chevelle bangs into things other than the Audi, hence the heavier damage.
here is little Effie's head
whose brains are made of gingerbread