Why did realism become a trend in literature?

Historically most literature of the past dealt with fantastical elements. Look at the Greek epics like The Iliad and The odyssey for example. Another one is the epic of gilgamesh, most of Greek Mythology, the Norse Saga's, Beowulf, Paradise Lost, The Divine Comedy, and all the gothic fiction that had horror/supernatural elements. It seems like historically there has always been a demand for fantastical stories. Yet in the 19th-20th century literature shifted more towards realism. With authors like F Scott Fitzgerald, Hemingway, Leo Tolstoy, Charles Dickens, Fyodor Dostoyevsky. Now I do like these authors and I enjoy classics and literary fiction myself. However I read fairly broadly and I read my fair share of fantasy. science fiction, and horror as well.

I'm just asking because when you look at history realism wasn't very common and people tended to prefer writing stories with mythological elements in them. Even going back to antiquity people preferred a hero with a big sword slaying a magical beast. To ask my question: why did realism take over literature?