Huck was the son of the town drunk. Didn’t have much schoolin’, didn’t have much Christianizin’. He pretty much brought himself up. Then he found himself on a raft with Jim. It didn’t take Huck much time to see a fellow human in Jim. Huck didn’t have no culture to speak of, and made his own decisions. His adventure was the adventure that America still is going through.
Twain did take for granted a lot of the things that the greater devoutness of the age made less escapable. He is said to have hounded the faith out of his wife... she shouldn’t have married the man if he was like that, but so went the story.