When Twain's autobiography was first edited he said of the process:
"“From the first, second, third and fourth editions all sound and sane expressions of opinion must be left out,” Twain instructed them in 1906. “There may be a market for that kind of wares a century from now. There is no hurry. Wait and see.”
Though it has been previously published, Victorian editors removed reference to anything society of the time would deem controversial, (refer back to Twain's comment above).
"In popular culture today, Twain is “Colonel Sanders without the chicken, the avuncular man who told stories,” Ron Powers, the author of “Mark Twain: A Life,” said in a phone interview. “He’s been scrubbed and sanitized, and his passion has been kind of forgotten in all these long decades. But here he is talking to us, without any filtering at all, and what comes through that we have lost is precisely this fierce, unceasing passion.”
More about what he didn't want people to know 'till 100 years after his death: