Why did Hashem say "they did not despise you"? Rather, they despised Me from ruling over them"?
Radak (5): If they would guard Derech Hashem, they would not need a king for war. I would fight for them! They did not despise you regarding judgment. They did not want a king for judgment; you sufficed for them. Now that they found an excuse to request a Shofet (because you are old), they requested a king, for they removed their trust from Me.
Malbim: A king can be submissive to Torah law and Mitzvos, like the early kings of Yisrael and current Nochri kings. Or, he can change the laws at his whim, like early Nochri kings. The Torah commanded a king "l'Vilti Sur Min ha'Mitzvah" (Devarim 17:20). "Melech Leshafteinu k'Chol ha'Goyim" (verse 5) can mean (a) a king to judge us [according to Torah law], like all nations. This merely insults Shmuel, that he did not judge like Torah law. Or, (b) a king, to judge us like Nochri kings do, who make laws according to their whim. If so, they agree that Shmuel judged like Torah law, but they rebel against Hashem and do not desire this. Shmuel judged them favorably (a), and was pained and insulted. Hashem told him "they did not reject you, rather, Me", like (b). 1 Had they intended (a), they would have said Melech k'Chol ha'Goyim Leshafteinu.
Malbim citing Sanhedrin 20b: The elders asked properly; the ignoramuses messed up. I.e. they said the same words, but with different intents. (Malbim explained that also the first way was insulting to Shmuel! Perhaps the elders requested 'a king to judge us based on Torah law, like all nations, and like you used to do, but now you are old and you cannot.' - PF)
