Why does Dorothea Brooke marry Edward Casaubon in Middlemarch?

In George Eliot’s Middlemarch, Dorothea Brooke marries Edward Casaubon primarily due to her own intelligence and idealism. She is a young, earnest woman who seeks a meaningful life and hopes to actively assist Casaubon, a middle-aged scholar, with his intellectual pursuits.12

However, this marriage is characterized as a serious error in judgment. While Dorothea enters the union with the noble intention of supporting what she believes to be significant academic work, she soon discovers that Casaubon is a pompous and ineffectual man who views her role merely as that of a secretary rather than an intellectual partner. Ultimately, the marriage serves as a central example of the "thwarted idealism" that defines the novel's exploration of human relationships and societal expectations.213