Oracle Bone Inscriptions in Shang and Zhou Dynasties was the earliest mature system of Chinese characters, but the number of characters at that time was very small.
At present, Xu Shen's Shuo Wen Jie Zi, which we have consulted and studied more, has only more than 9,000 words.
What's more, the earliest words must be even less pitiful.
Think about it. How can I express more meaning with so few words?
In this way, "variant characters", "interchangeable characters" and "ancient and modern characters" have been formed.
It takes several words to express a lot of content, and then a word will appear and be used in many articles.
The same word has different meanings in different articles and so on.
Of course, society is progressing, time is passing and writing is developing.
More people will create and change words for the convenience of expression, and later generations will find more commonly used words.