Good question. The question revolves around the fact that Satan was around God. The point here is that Satan was not legally condemed, because there was no proof that he was the one doing all the bad actions. Sure, God knows that he did it. But in order to properly condemn Satan of his sins, which came to the sacrifice of his only son, Jesus. This is where crucifictioncrucifixion comes from. In order to be a witness of Satan's sins, he had to be crucified. Why do you think Jesus was hesitated in prospect of being crucified? It is not because of pain, but the prospect of having to face the revolting hatred and sins of Satan, directed towards Jesus. Think, Jesus is repulsed by the sins. When he was hung on the cross, and when God turned away from Jesus:
46 About three o'clock Jesus cried out in a loud voice, "Eli, Eli, lama sabachthani?" This means, "My God, my God, why have you abandoned me?"
At this, Satan took the chance and took his hatred out on Jesus. Since nobody was looking, he took at as a chance. However, what he had not expected was for Jesus resurrecting. Since he was resurrected, Jesus became witness for Satan's sins, and was able to fully condemn him.
However, it is certain that Job was written before this, however there is no exact pin-pointed location of when. But looking that the original text, it is safe to assume that story of Job occured at the time of Abraham, if not Isaac and Jacob. From there it seems to be that it occured during Jacob's generation. Satan was officialy rebelled, but he was still at the point able to condemn us through the Laws of God, him being not condemned through it before the crucifictioncrucifixion.