Answer: As the Creator, God would have known that Lucifer and other spirit beings could rebel. Yet God did not make this choice. It was Lucifer who chose to try to exalt himself above God's throne. He made that choice to rebel—to become Satan, the adversary.
Satan was and still is the chief or ruler of the fallen angels. Isaiah 14:12-14, "How you are fallen from heaven, O Lucifer, son of the morning! How you are cut down to the ground, you who weakened the nations! For you have said in your heart: 'I will ascend into heaven, I will exalt my throne above the stars of God; I will also sit on the mount of the congregation on the farthest sides of the north; I will ascend above the heights of the clouds, I will be like the Most High.'"
From the creation of mankind, Satan and his demons were actively rebellious against God and man. It appears that pride was the source of Satan’s downfall.
Lucifer was obviously puffed up with pride, even exalting himself above God’s throne. This is a good lesson for all of us as we listen to radio and TV religious broadcasts that put on a good show but may not be preaching the truth.
2 Corinthians 11:13-15, "For such are false apostles, deceitful workers, transforming themselves into apostles of Christ. And no wonder! For Satan himself transforms himself into an angel of light. Therefore it is no great thing if his ministers also transform themselves into ministers of righteousness, whose end will be according to their works." That is also why it is important to prove all things.
God gave Satan permission to test Job. Job 1:8-12, "Then the LORD said to Satan, 'Have you considered My servant Job, that there is none like him on the earth, a blameless and upright man, one who fears God and shuns evil?' So Satan answered the LORD and said, 'Does Job fear God for nothing? Have You not made a hedge around him, around his household, and around all that he has on every side? You have blessed the work of his hands, and his possessions have increased in the land. But now, stretch out Your hand and touch all that he has, and he will surely curse You to Your face!' And the LORD said to Satan, 'Behold, all that he has is in your power; only do not lay a hand on his person.' So Satan went out from the presence of the LORD."
God clearly used Satan to test and provide difficult trials for Job. We need to be aware that these demonic spirits exist, but—guess what?—it is OK for us to disbelieve these spirits. If something doesn’t seem right, we should put them to the test. 1 John 4:1, "Beloved, do not believe every spirit, but test the spirits, whether they are of God; because many false prophets have gone out into the world."
We need not fear that the Devil will overcome us and ensnare us in his rebellion, as long as we stay close to our Savior.