What did Israel know about the other nations who had kings?
Israel knew that the surrounding nations who had kings were pagan and idolatrous. They understood those peoples worshiped idols and did not know the one true God; only Israel had that knowledge. Despite this, the elders still demanded a king so they could be like everybody else.
Les explains that when Israel asked Samuel for a king, they wanted to be like all the other nations around them. He notes Israel well knew those nations with kings were pagan and idolaters. No one but Israel had a knowledge of the one true God. God had called Israel through Abraham and Moses to be different, a sanctified, set-apart people, not to be like the rest of the nations. Their request rejected Jehovah, not merely Samuel.