Flannery O'Connor was influenced by several Southern writers of great repute, like William Faulkner and Eudora Welty, as well as Modernist writers like T.S. Eliot and Joseph Conrad. These are only four writers of many who may have had an influence on Flannery O'Connor.

Though O'Connor did not write in the same style as Faulkner, whose approach was much more realistic than O'Connor's, they share many characteristics of Southern literature. Both O'Connor and Faulker explored violence in a particularly Gothic way, perhaps channeling the darkness of losing so many Southern lives in the Civil War, all for very little gain.

Eudora Welty is another Southern writer that influenced O'Connor. Both writers embrace ordinary-seeming events that impact rather ordinary people. O'Connor's characters seem to experience much more macabre instances than Welty's, but they often start in similarly regular circumstances.

Modernists like T.S. Eliot and Joseph Conrad may have inspired O'Connor to experiment with style and substance. Both Eliot and Conrad are credited with unique writing styles and a way with language that can sometimes be confusing, unexpected, and deliberately difficult. O'Connor's style is rather straightforward, in contrast, but her subject matter is often jarring, which gives it a Modernist feel.

According to critics there were three strands to the reality of Flannery O'Connor:  literature, the South, and Catholicism.  And, it is the combination of these three strands which makes O'Connor unique.  O'Connor concerned her writing with the "reality of spirit permeating matter." Her short story, "A Good Man is Hard to Find," the grandmother's spiritual recognition of her similarity to the Misfit as a sinner like him exemplifies this concept. 

There is a depth to O'Connor's writing that comes from her rich experiences in personal and spiritual life.  She had numerous personal and professional relationships, attended Catholic schools as a child, and then went to colleges in her home state of Georgia and later University of Iowa.  Following her graduation from college, she moved to an artists' colony in Saratoga Springs, New York.  After she was diagnosed with lupus, from which her father had died, O'Connor returned to her hometown where she enjoyed raising ducks and peacocks.  The peacock is a prevalent symbol in her narratives, representing beatific vision, the goodness of mercy.

Flannery O'Connor's religious beliefs and her fatal illness also provide some insight into her fiction.  In his essay "The Dark Side of the Cross:  Flannery O'Connor's Short Fiction," Patrick Galloway suggests her contributions as

cathartic bitterness, a belief in grace as something devastating to the receipient, a gelid concept of salvation, and violence as a force for good.

O'Connor's anti-parables drawn from her experiences, faith, and unique sense of humor, "show the way by elucidating the worst of paths," writes Galloway.

What at first seem senseless deaths become powerful representations of the swift justice of God, the self-deluded prideful characters that receive the unbearable revelation of their own shallow selves are being impaled upon the hold icicle of grace, even if they are too stupid or lost to understand the great boon God is providing them.

Her Catholic faith was reconciled to her fiction in her proving "the truth of Faith." O'Connor felt that the average Catholic mind separates nature from grace, thus perceiving the fictional depiction of nature as sentimental or obscene. But, because she believed that sentimentality was an excess, Nature is used in O'Connor's fiction to emphasize the negativity in the lives and mental states of her characters.  Galloway writes,

Nature in O'Connor's stories reflects mankind, in all its base nature, and it is in keeping nature constantly in view that the author avoids the sentimental, and its flipside, the obscene.

Likewise, in an apparent incongruity with her deep religious faith, O'Connor uses the grotesque and violent, but she haa contended that she has used them in the service of a greater vision of spiritual reality.  Compassion to O'Connor was an excusing of human weakness.  So, she showed the way by using "the worst of paths."

What Thing/things Caused Flannery O'Connor to write the things she wrote?How her life influenced or affect her writings

Flannery O'Connor was truly a genius and an extremely gifted writer. I think that there are two major things in her life that influenced her writing; her religion and her disease. She was a very religious Catholic, although the trappings of religion were less important to her than her faith. She also suffered from Lupus, an inherited disease that also killed her father. She died when she was only 39 years old.

If you do some research, you can find many interviews in which O'Connor explains how she incorporated her faith in her short stories.

Living with her impending death caused her to contemplate the unfairness of life. This comes out in her stories. Also, she was conflicted over how a loving God could allow evil and suffering in the world. This caused her to write depressing and complex fiction with multi-layered themes and complicated characters.

You can read about her hereon eNotes.