No - you don’t understand the simple concept that most accidents can be prevented.
I agree that accidents can be prevented. But you said its not an accident if someone trips over an electrical cord left on the stairs. So moving the cord would prevent someone tripping but, by your logic it would not have prevented an accident.
I would say someone tripping over a cord that someone else did not move is an accident. You do not agree: “An accident is something that could not be prevented.”
But despite saying that you go on to call the trip an accident “If you see a coiled up electric cord on the stairs you should move it because it might cause an accident if somebody else trips over it.”
“If you don’t move it and somebody trips and gets hurt it wasn’t an accident because it could have been prevented by the person not leaving it there or you when you noticed.”
So is the tripping an accident or not?