Venom looked back when he felt a tug on his web line. Spider-Man was trying to force the car back down. Why wouldn't he want the car to stop? Venom gave a strong, forceful tug on his web line, confident that his greater strength would overcome Spidey's attempt. To ensure that the car stops though, Venom just let go of his swinging web allowing himself to fall through the air aiming to land on the flipping car in mid-air. It's a tricky maneuver, but sounded like a fun idea that Venom wanted to try.