What is the Biblical basis that Mormonism is the only true and living church upon the face of the earth?

This revelation was given to Prophet Joseph Smith in 1831 and can be found here in [Doctrine and Covenants 1:30](https://www.churchofjesuschrist.org/study/scriptures/dc-testament/dc/1?lang=eng) . I ask this question because the entire body of Mormonism, 100% of its "scriptural" content (apart from its borrowings from the Bible) is fully and exclusively traceable to and or dependent upon exactly and only one source: the claims of one man - Joseph Smith. He is the single, sole source of the Mormon "revelation," why should we believe him? Why do Mormons believe him?