Leonces's flaw as a husband is the result of his belief in the traditional roles of Acadian society and of his unwillingness and inability to communicate effectively with Edna.
As a "traditional" Creole gentleman of the times, Leonce believes it is his duty to provide financially for the family and it is Edna's duty to be devoted to him, their two children, and their home. When Edna suggests she is not interested in these domestic duties, Leonce is almost incapable of comprehending what she means. In his mind, this line of thinking is utterly ridiculous. In short, Leonce does not think of Edna as an equal partner in marriage or in life, he thinks of her merely as another member of his employ.
Against that backdrop, Leonce's inability to communicate effectively with his wife exacerbates the problem. When Edna shares her feelings with Leonce, he dismisses them. When her behavior contradicts his expectations, he dismisses them as well, choosing to believe that it is simply a phase through which Edna will pass. By dismissing Edna and her concerns and never communicating with her about them, Leonce severs any ties that exist between the two.