Why did the angel Lucifer rebel against God?

Pride and self-importance caused Lucifer to rebel against God. Lucifer wanted to be like God and set out to overthrow His kingdom. It has been a fierce, unending battle ever since. Mankind has tragically inherited the same prideful propensity.

"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 to heaven; I will exalt my throne above the stars of God; I will 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’" (Isaiah 14:12-14).