1. Let's talk about inevitable events first. Generally, it is inevitable to be greatly influenced by objective factors such as technology and environment. The most typical example is the transformation from matrilineal clan to paternal clan, which eventually formed a patriarchal society for thousands of years. The reason for this is not difficult to understand, so I won't go into details.
Another example is the merger and division of countries. The so-called combination will be combined for a long time, and it will be combined for a long time. This is also an inevitable phenomenon. Simply put, the development between neighboring countries is not completely balanced, leading to merger. However, the result of the merger will lead to the country's size beyond the scope of science and technology and politics, and it will definitely split. China has always had the highest political and economic level in ancient times, which is why China has always maintained its national scale. On the contrary, countries in backward places are relatively small, such as Africa, and there were few unified countries in ancient times.
2. But many things are random or decided by heroes. Simply put, microscopic things should be random. Macro things should be inevitable in general, but there are exceptions, such as the choice of culture and political system, which is more complicated.
In fact, it is quite accidental that we see that the East and the West chose almost completely different political models in ancient times. If there are Confucius and Laozi in the west and Plato in the east, perhaps the choice of system is inevitable, but such figures have only appeared for thousands of years, and this scarcity has led to accidents.
Generally speaking, history has certain inevitability, and it is also determined by heroes to some extent. But these heroes are not overlords who dominate the world, but really scarce thinkers and politicians. I'm sorry for the rush and confusion.