u/Batmaniussus

So as we know Marty Starts to disappear in this scene because George didint Kiss lorraine, however he does a few seconds later. So my question is why Marty Starts to disappear because in Order for him to disappear it should have Never come to the scene where George kisses lorraine without martys help. Now if we would say that he Starts to disappear when the Future Isint sure that it is going to Happen that Marty is Born, he should have started to disappear as soon Lorraine had a crush on him.