How did God end up giving Satan the power in the first place? Is it permanent? Then what?
(So everyday we must live in Christ to avoid yielding earthly authority to Satan.)
Meanwhile, Christ proved that man (a "son" of man) could live a sinless life *till death* thus Satan is put on trial for high treason, where he's kicked out. Then he'll be arrested & jailed (1000 years in the pit), and then released to make his closing argument ("try to tempt the world again"), only to be sentenced (destroyed) in the end.
...however...
Only by the testimony of 2 or more witnesses can any matter be established (as true). Christ proved that man could resist temptation, live righteously till death and that Satan is guilty...but legally Christ's sole testimony isn't enough to convict Satan (as God is *perfect* Justice)...that's why even though "it is finished" and "[he] saw Satan fall like lightning", Satan MUST be allowed to perform his piece-de-resistance of deception to prove Christ's testimony without a shadow of a doubt. So we've still got remaining drama to finish in this story.
Not having much time left, this is the reason for the layers & layers of deception and distraction. Only those who have "the testimony of Christ" (like those apostles of the 1st century) will finally prove Satan guilty (as "the witnesses"), but if he can manage to keep everyone blinded, deceived, distracted and entertained (he hopes) that day may never come, proving Christ's testimony isn't true.
Anyway, this is what I've pieced together standing on biblical principles...