It is towards the end of this tale that we find the answer to your question and Clarence reveals his plans for the royal family of the new republic Hank wishes to form. Initially, he wishes to have a royal family made up of humans, however, when Hank tells him that "kings were dangerous," Clarence suggests that they should have a royal family of cats. We can see Twain's typical satirical reasoning coming through in his reasoning:
He was sure that a royal family of cats would answer every purpose. They would be useful as well as any other royal family, they would know as much, they would have the same virtues and the same treacheries, the same disposition to get up shindies with other royal cats, they would be laughably vain and absurd and never know it, they would be wholly inexpensive, finally, they would have as sound a divine right as any other royal house, and "Tom VII., or Tom XI., or Tom XIV by the grace of God King," would sound as well as it would when applied to the ordinary royal tom-cat with tights on.
His reasoning continues, but you can get an idea of his thoughts and why he thinks this would be an admirable solution to the problem of having human kings. We see here Twain's satirical view of the Royal Family, its function, purpose and character, which asks serious questions about its use in a comic fashion.