If Satan was / is such a bad character, the worst of all, why not kill him in order to protect "your" people?
https://www.vocativ.com/news/309748/all-the-people-god-kills-in-the-bible/index.html
There are 160 separate killing sprees in the Bible for which God is demonstrably to blame. That number includes every slaughter in the Old and New testaments, and also in Aprocrypha, the contested books which are included in the Roman Catholic Bible but disregarded from the Hebrew version. A total of 2,821,364 deaths are specifically enumerated in scripture as either directly orchestrated by God, or carried out with his assistance or approval. Satan, on the other hand, notches up only 10 kills.
Most of the time, God is a big fan of the Israelites. The Lord plays some part in killing 1,050,009 of the their enemies throughout the good book—a big assist. They do their part, though, righteously slaying 1,540,494 people in the name of the Lord for wrongs against them. The Bible’s biggest individual assassin is David, the second king of the United Kingdom of Israel and God’s favorite monarch, who smote, slew and slaughtered 81,050 people on the Lord’s behalf. In 2 Samuel, he carries out what is arguably his most grotesque killing—and that’s saying a lot, considering David commits massacres and genocides in a single book. In order to buy a daughter from Saul, the first king of Israel, and make her his wife, he gifts him 200 Philistine foreskins. “David arose and went, he and his men, and slew of the Philistines two hundred men; and David brought their foreskins … And Saul gave him Michal his daughter to wife.” (2 Samuel 18:27). Quite the dowry.