Marcellus tells us "Something is rotten in the state of Denmark." After we hear the ghost's message, how does this prove true in a broader sense for the whole country?

This is one of the most famous lines in Shakespeare's work. "Something is rotten in the state of Denmark " refers both to the spiritual and political corruption in Denmark. The new king, Claudius, obtained the throne by murdering his brother. Moreover, he is in incestuous marriage with Gertrude. The king is obviously more concerned with keeping the plot against his brother a secret, than actually ruling the country. Hamlet himself makes a similar remark in Act I, Scene II, comparing his country to a neglected garden: "Tis an unweeded garden."