Hosea 13:10

‘Where now is your king,

That he may save you in all your cities?

And your judges, of whom you said,

Give me a king and princes?'

Let them consider that their king and princes have already been snatched away by the wild beasts. Where were they now? If this was just prior to the siege of Samaria, Hoshea, who had gone to the Assyrians to parley, was already in their hands, while many of their princes would have been captured in the fighting, both in defending their borders, and in defending their other cities which had already been destroyed. Thus there was no one left to save them as they waited helplessly in their cities. All the folk around would have crowded into these cities once the invasion came (compare Leviticus 26:25), looking for their king to come and save them. That was why they were built with stout walls. But they could not resist a determined invader.

However, the question may be asking where their king was simply because he was proving to be impotent in the face of the enemy. The implication is that whoever their king and judges were, they would be unable to save them. They had trusted in them, but they could not help them (while in contrast YHWH could - Hosea 13:9).