One of the reasons are Hamlet wasn't claim king after Claudius death. The reason for revenge was for to avenge his father's death and continue his legacy of the throne. He wasn't able to get the throne because he was poison by Claudius. It was a heartbreaking moment for the people in Denmark.
Second reason was that Claudius didn't felt scared. After the play Claudius been after shameful and pathetic after the "The MouseTrap ". Claudius was willing