You change something in the past everything is changed in the future. My theory..
For instance, in a Football match, you see someone miss a free kick and the goalie catches it. Turns out the team which missed the free kick loses 2-0. And you say "if they made the free kick they woulda won!" wrong, because if they woulda made it in, it would've changed the whole outcome of the match. The same play doesnt continue from a goalie box kick out thing, as it would do starting from center kick off. If I make myself clear... That's my view, anyway..