Kay Kavus holds the throne for most of the heroic age, and the Shahnameh's verdict on him is that a crown is not the same thing as judgement. A minstrel sings to him about how beautiful Mazandaran is. Everybody in the room knows what is over that mountain wall. He orders the march anyway.

That is the pattern. He tries to fly, on a throne lifted by eagles. He believes the wrong people about Siyavash, who is his own son, and puts him through fire to prove something that needed no proving. He starts a war he cannot finish and has to be got out of it.

The poem does not make him a villain, which is the hard part. He is the ruler in good faith who keeps being certain, and Rostam is the one who has to go and undo it. The road of seven stages exists because of a decision this man made in an afternoon.