In #deuteronomy 17:14, God told Israel that they could have a king if they wanted. Contrast this with Samuel's disgust when Israel demanded that he give them a king a few hundred years later. The problem wasn't that they wanted a king, but their reasons for wanting one. They didn't trust God. They feared the kings and armies of their neighbors and thought they needed their own to be secure.
It's not a sin to want a king. In fact, we're supposed to want a king, but the king we should want is #yeshua (aka #jesus), not Saul, and not even David.