Lots of people get sued for lots of things. Nowhere does it say that suits can succeed only if the defendant is the sole cause of the problem. See: Takata air bags. Huge liability, but in any given incident it wouldn’t be a problem unless someone else caused an accident. Yet Takata does not get to say “or defective product wouldn’t have been a problem if Mr. Doofus hadn’t rear-ended you”
Binary is great for computers, less good in legal thinking.