Of course he worked in his life - he worked on boats on the Mississippi
He also worked at a printing press, and a lot of other jobs. Later, he became a writer, and if you don’t think that’s work, try tossing off a novel one afternoon in your spare time.
Many prominent writers have questioned the authorship of Shakespeare’s work. I don’t agree with them, but it’s not ipso facto an indication of stupidity or evil.
IIRC Moby Dick predated Huck by about 30 years. There's also Nathaniel Hawthorne.
That said, Clemens is clearly an American treasure.