Hamlet and reality

I find it interesting how Hamlet plays with the idea of a play within a play and extends the idea to the characters themselves: Hamlet is a character pretending to be insane, Claudius is a murderer pretending to be a just ruler, and it’s never made clear whether Gertrude really believes Claudius’ story, or if she’s just a gold digger. I wonder if perceptive playwrights such as Shakespeare have a special insight into human behavior. Maybe after inventing a certain number of characters, they start to see through people, and life itself starts to seem like a play.