It's Not Always About the Main Character
Despite the common misconception, not all stories revolve solely on the main character. Sometimes, it's about the supporting characters, too. Take the popular series Harry Potter, for example. Though the whole series revolves on the thoughts and experiences of a particular main character named Harry Potter and his friends as well as their battle against the evil Voldemort, we realize towards the end of it that Snape, the seemingly antagonist character in the series, is perhaps the main character after all. Despite being behind the storyline all throughout the seven books, Snape's character has done invaluable help in furthering the plot of the series. Despite being hated by fans, they realized in the end that he was an indispensable character. We pitied him for his sacrifices and respected him for his efforts, recognizing that perhaps he was a main character worthy of his own story, too.
Let's take The Lord of the Rings Trilogy as another example. Here, we assume that either Sauron the ""Lord of the Rings"" or Frodo the ring-bearer is the main character of the trilogy. Personally, I think that either the ring itself or Smeagol, also named Gollum, is the main character. The ring, being naturally evil, only answers his master. A Fellowship composing different races in Middle Earth is formed for the sole purpose of destroying it, even resulting to the death of some. The plot starts and ends with the creation and destruction of the ring. It has spanned hundreds of years and has seen a number of owners, one of which is Gollum. Gollum can also be a main character in his own worth. He has lived because of, and for the, ring. It was thanks to Gollum that the ring came to Bilbo, who passed it to Frodo. After their long journey across Middle Earth, the ring-bearer hesitates moments before throwing the ring into the fires of Mount Doom. Again, it was thanks to Gollum that the ring was eventually destroyed.
In these two popular literature of the generation by J.K. Rowling and J.R.R. Tolkien, we have seen how not all stories are about the main characters themselves. Sometimes, supporting characters are main characters on their own rights. After all, everyone is the main character of their own story.