Why do the crooked King and Duke give the money to the girls?
The fraudulent king and duke are pretending to be the deceased Peter Wilks's brothers and the true heirs to his sizeable fortune. In this way they aim to to cheat Wilks's three daughters, Mary Jane, Susan and Joanna, out of their rightful inheritance. However, they give the money to the girls at first, because at this stage they're making a great show of caring about them and getting everyone on their side, and they plan to steal the money back later anyway. They certainly manage to fool most of the townspeople for a time - and in fact the girls are so taken in by their show of sorrow and sentimentality over Peter's death that Mary Jane actually hands the money back to them, saying that she trusts them completely. Huck, who is forced to go along with the king and duke, is absolutely disgusted with the whole thing, and resolves to reveal the truth to the girls.