system
Given the following post, respond as if you're commenting on Reddit:
human
[A Sound Of Thunder] How Exactly, Does Stepping On A Butterfly In The Cretaceous Change History So A Dictator Wins An Election In The Present Day?

(The original Ray Bradbury Story, not the godawful movie)

In any time travel story, it's important to remember the rule of 'the correcting river of time' where if you go back in time and try to change something, history will try to make it so history is as much like it was before you left. If it applies to one story, or doesn't. 

For example, if I time travel back to the cretaceous period and abduct a bug to bring to the present for a science project. It will either do one of two extremes.

1) Nothing, my change to the timeline will have done nothing because the timeline will be inherently resistant to change. The timestream will make it so that no changes I make have an affect on humanity evolving.

2) I will return to a timeline where Humanity never evolved and Lizard people became the dominant species.

So how then, does someone stepping on a butterfly in the cretaceous, not change the evolutionary pattern of human history. But results in a different winner of a presidential election? Two events that have seemingly no connection at all?
gpt
A descendant of that butterfly would develop a genetic mutation that would lead to the caterpillars of its offspring becoming a major pest if a certain plant species. Later on that plant species is developed as a human crop species.

What a particular administration decides to promote that crop as part of their agricultural policy, the presence or absence of that pest could make the difference between the success or failure of that policy, leading to the rural vote swinging toward or away from that party at the next election.

The minor changes in langage also mentions in the story could ne due to an avid young butterfly collector twisting an ankle whilst in persuit of an example, and discovering a love for linguistics instead whilst recovering, and so ending up writing an influential book on spelling reform in previous generations. If he hadn't done that, he might have noted the potentially disastrous effects of the caterpillar on that crop...