How did they predict it?

That is judged according to certain conditions.

Including:

1. The objective law of things' own development, such as breaking a cocoon into a butterfly, is the law of existence and will inevitably decide to become a butterfly.

2. The objective conditions for the development of things. For example, there are many factors that can stimulate an event, and the probability of an event is greater.

3. The changing trend of things in different stages is influenced by natural and social conditions.

4. The exertion of people's subjective initiative. This is very important. Man is a clever animal, who can know the world and change it. According to the inherent laws and relations of things, people know the essential laws of things and create new relations on the basis of the original relations.

If the first three are the foundations, human efforts are the key, which is why everything depends on human efforts.