Why does Natalya become disillusioned with Dmitry Rudin?

In Ivan Turgenev's novel Rudin, the heroine Natalya becomes disillusioned with the titular character, Dmitry Rudin, because of his inability to translate his eloquent rhetoric into meaningful action.

While Rudin captivates the younger members of a provincial salon with his powerful oratory and passionate advocacy for progress, his character is defined by a gap between his words and his deeds. When Natalya falls in love with him and challenges him to live up to the high ideals he professes, he fails to meet her expectations, ultimately proving unable to act upon his convictions.12