There are many limits to human cognition. One of those is limits to levels of intentionality. Mark Kohn explains at Aeon, referring to the work of Robin Dunbar:

As Dunbar has pointed out, Shakespeare’s Othello requires audiences to believe ‘that Iago intends that Othello imagines that Desdemona is in love with Cassio’. That takes them to four levels of ‘intentionality’, or mental representation, but not to an especially compelling story. To bind the narrative spell, Shakespeare has Iago persuade Othello that Cassio reciprocates Desdemona’s feelings. This raises audiences to a fifth level, which is about the natural limit for most people. (In order to tell the tale, Shakespeare himself would have been operating at the sixth level, which is beyond most of us.)