I think the play makes it quite clear that it is the irrational jealousy of Leontes that is responsible for the problems that he faces later on in the play after he has acted on that irrational jealousy. The situation that Leontes faces seems to be one of his own making. Let us remember that in Act I it is he that asks his wife to intercede with Polixenes to ask him to stay for longer, and then he turns around and suspects her of infidelity after he has pushed them together. Note how the irrational nature of his jealousy is stressed by the way that nobody shares his suspicions. When Leontes tells Camillo, for example, Camillo does not believe that this could be possible. Even in Act III when Hermione is formally tried for adultery, Leontes ignores the words of the oracle that protests Hermione's innocence and proves that she is chaste and has been loyal to her husband. It is the determination of Leontes to act on his own irrational and unsupported suspicions that threaten his own downfall and results in the death of his wife and his estrangement from his child.