Mark Twain's Influence On Human History

I am skeptical about speaker's assertion that the greatness of individuals can be only judged by those who live after them, not only by their contemporaries. Didn't Mark Twain become a famous novelist and a household name in his life time? Didn't Mozart's music gain people's appreciation in his short-lived 35 years? And didn't Albert Einstein obtain other scientists' identification when he created the theory of relativity?Admittedly, in the human history, there were many great persons didn't get his merited admiration in his contemporary era. But this phenomena is normal because sometimes the great man's achievement and theory totally exceed ordinary people's ability of understanding, even more some of them challenge the authority and tradition. Nicolaus Copernicus, the Poland astronomer and the father of modern astronomy, he didn't publish his theory of solar system until died, just because he was fear of inquisition's persecution. And Giordano Btuno who is the great Italy philosopher and ideologist, was executed by the inquisition
Everything changes. Along with societys development and technology's advance, people's mind is more open than before, and people's knowledge is more advanced than predecessors. And a democratic society could support us an equal and unrestricted space to pursuit our dream, to advocate our assertion, and to fight for our rights. For example, American black leader, Martin Luther King who published the famous speech---"I have a dream" to 250 thousand people in front of the Lincoln memorial, he combated the discrimination and fight for human rights, as a result, he got the Noble Prize of the Peace in 1964. It is impossible to imagine that happen in the past of Btruno and Copernicus' time, though his death is a tragedy. From this example, we learn that the key point of deciding an individuals' greatness is not about time but people's mind and society's