Why does Mrs. Crater want Mr. Shiftlet to marry Lucynell?
Even though both Mrs. Crater and Mr. Shiftlet profess the importance of spirituality in their lives, they make decisions based on material needs and wants. Mrs. Crater needs a caretaker for her property and has nothing to offer other than her daughter Lucynell. When Mr. Shiftlet arrives, the property is run down and the Ford automobile in the shed doesn't run. Mrs. Crater suggests that there hasn't been a man around for fifteen years and, once she knows that Mr. Shiftlet, despite having only one arm, is capable of fixing anything, she is eager to get him to marry her daughter. At one point O'Connor writes that Mrs. Crater was "ravenous for a son-in-law."
Lucynell is deaf and dumb but is able to do simple chores around the house. She is indispensable to her mother, not only because of the work she can do, but almost certainly because they have been together for so long. Mrs. Crater claims the girl is only about fifteen but she was really closer to thirty. Because she is mentally challenged, the girl is unable to control her fate and becomes a pawn in the absurd negotiation which goes on between Mrs. Crater and Mr. Shiftlet. Mrs. Crater is selfish in wanting to use her daughter simply to get a handyman. She lures Mr. Shiftlet into marrying Lucynell with the promise of money and the use of the car. Likewise, Mr. Shiftlet uses the girl in his quest to rob Mrs. Crater of her money and the car. As soon as he leaves the property he dumps Lucynell at a roadside café.
Mrs. Crater has various reasons for wanting Mr. Shiftlet to marry Lucynell. Mrs. Crater leads a very sedentary life and depends on her daughter to cook, clean, feed the chickens, do the laundry, grocery shop and care giver jobs on the plantation. To get a son-in-law, she could have a full-time chauffeur, a laborer, a carpenter, mechanic, farmer, etc. She would have the best of both worlds and wouldn't have to want for anything. Whoever marries her daughter would have to stay on the farm because her mother would not be able to do any of the self-help skills the daughter does for her. Mrs. Crater is being very selfish in her desire for a son-in-law.
Mrs. Crater wants to secure the handyman skills of Mr. Shiftlet, and so tries to bribe him with material goods in order to unite him to her daughter.