1)
Why did they say "you grew old"?
1.
Radak: You cannot judge us like you used to.
2)
Why did Yisrael request a king when Shmuel grew old?
1.
Radak (7:13): He went around Yisrael and rebuked them, until his old age when he could not. Then, they sinned and Pelishtim attacked, and therefore they requested a king. Had they not sinned, they would not have needed a king. This is why Hashem was displeased. However, at that point they needed a king, like Hashem told Shmuel - "u'Meshachto l'Nagid... v'Hoshi'a Es Ami mi'Yad Pelishtim" (9:16).
