What events and phenomena formed the basis of ancient myths and legends?

The basis of absolutely all, not only ancient, myths and legends became famous historical identities, extraordinary real events. These could be outstanding rulers and kings, storms, hurricanes, sweatshops, volcanic eruptions and the like. Also, the myths often laid the desire for people to explain incomprehensible phenomena. So, for example, there were stories about the creation of the world. Often the basis of mythology became the legends of other peoples. So, the Greeks used Sumerian, Eastern, Mesopotamian and other sources.