Mythologies of many different cultures all seek to explain various natural phenomena with a story. Greek myths often attempt to explain the reason for hard to understand concepts like what happens after death, why it rains, or why people with extraordinary talents exist. They are often tools to teach moral or social lessons, explaining what might happen should you deviate from the right path.
An important part of the genre of mythology is the stories that explain occurrences in the natural world and in human nature. Most mythologies predate scientific discoveries and modern understanding. It may seem unrealistic to us now to ascribe a great thunderstorm to the anger of a god. However, it was far easier to explain thunder and lightning as divine punishment from a sky god rather than understanding the changes in temperature, pressure, static electricity and the water cycle.
In Greek mythology, the gods and goddesses are essentially humans (anthropomorphized beings) with varied and amazing supernatural powers. All the gods have personalities like humans, get angry like humans, show kindness like humans, and act spitefully like humans. The big difference is the gods and goddesses have power so great, that their personalities, anger, kindness, and actions all have an effect on people and nature. Natural occurrences are more relatable and easily understood when the causes are driven by the emotions by powerful gods.