How does Huck ruin the Duke and King’s plan? Why does he do it?

The Duke and dauphin pretended to be the brothers of the recently deceased Peter Wilks in order to obtain his money and property. The Wilks give them 6,000 dollars in gold. Huck doesn't like this type of trickery so he steals their 6,000 dollars and hides it in Peter Wilks' coffin. He then tells Mary Jane Wilks what has been going on. Huck instructs her to stay at a friends house for the night to allow him time to runaway. Here was this family that just suffered a great loss and the Duke and dauphin decided to take advantage of their feelings. Huck didn't like this at all. He felt bad that they were tricking this family in order to get money. This was a turning point to Huck because it showed some maturity. Throughout the book Huck has played tricks on people, and now we see that he doesn' want to.