>> “Now answer this, what was Satan’s sin; in other words, why was Satan cast from Heaven?” <<
Contrary to popular confusion, Satan has not yet been cast out of heaven. That happens at the mid point of Daniel’s 70th week.
That event is likely to come soon, and when it does, you will see “Antichrist” stand on the Holy Place of the mercy seat of the Ark, and declare himself to be God.
Until then, he remains in the throne room accusing the believers.
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Good point. The non-temporal nature of God can make things a bit confusing at times.