Why do you think Twain put a description of the circus here? How would you compare the circus to the entertainment provided by the duke and king?

Twain included the circus as a comparison to the duke and king's entertainment.  The circus showed how not smart Huck was.   Huck was worried about the people in the circus, because he did not know the performers were trained.  The circus was fun and entertaining for everyone.  The duke and king provided rip-off entertainment to men.