According to the passage, it can be inferred that Elizabeth Cady Stanton's personal qualities, particularly her ability to write and speak, helped get the movement's message heard by the public. The passage highlights her "verbal brilliance" and her capability to articulate the ideas of the women's suffrage movement, which were essential for communicating the cause effectively. Therefore, the most accurate inference is:
Her ability to write and speak helped get the movement's message heard by the public.