One of the reasons that things keep changing, even if they’ve already changed before, is that the effects are propagating outwards and causing secondary and tertiary changes in their own right. If smoking ads were banned two decades earlier, then up to a million people might never have gotten lung cancer. As the mandala effects work their way through our timestream, whatever difference they or their children made in the world these resulting changes start to show up in our world.
Propagating effects apply to any changes that would have long lasting effects in the world, including the millions of people who ended up not dying in various wars and conflicts that in the adjusted timestream caused much fewer casualties or never happened at all, the technological advances that came from color TV being invented decades earlier, and the influence this had on art and human development.