How can one event change everything?

One event can lead to many other events, also known as the butterfly effect! for example, if a mom and her kid were in a room with a jar of cookies. the mom says not to eat a cookie when she leaves, but the kid doesn’t listen and takes one anyways. at the time it isn’t a big deal, but this can lead to lack of trust, and change their relationship. this is an example of one event that could lead to others.