He had iniquity or sin in him. Basically, he had illusions of grandeur, thinking he would supercede God, Himself and rise above Him. He was literally kicked to the curb, falling straight to earth like a comet, and poisoning the perfect world God had created for us. This is why we battle with sin. Our physical bodies are composed of the dust of the subsequent poisoned earth.
The thing is, God made an out for us, through Jesus Christ; because He created us like Him - as spiritual beings first, then put our spirits into the clay body form. It is our spirit, and the spiritual connection to God that enables us to escape the degradation Satan inflicted on this world with his presence; which he tries to inflict on us as well.
Only if we stay connected to God, and develop a strong relationship with Him, can we overcome our base desires of the flesh (this poisoned clay body) and only by that connection through His son, Jesus, can we escape the fires of hell and go to heaven. Those who fail to make this connection, will suffer death physically, and then spiritually in fire because fire is a purifier. Seek Christ and draw closer to Him, and you will have eternal life.
Btw...Lucifer and Satan and Beelzebub are one and the same. FYI.