If Jesus effectively destroyed the works of the Devil (1 John 3:8b) why does death remain?

Death remains because of the curse (Romans 5:12; Ezekiel 18:20) and God’s faithfulness to His word; death of the body will manifest for disobedience as God warned in The Beginning but God’s objective does NOT focus upon the flesh but on the spirit of man created in His image (Genesis 1:26-28).

We ARE spiritual beings encapsulated within a decaying body of flesh; this body of flesh is only a temporary “tent” for God’s purposes (2 Corinthians 5:1) in a World constrained by Time and physics and that tent will be torn down by death but the spirit remains…again…this existence within the Realm of Time and physics is simply an object lesson and we’re players in the midst of an unfathomable cosmic struggle that is rooted in the spiritual NOT the carnal.

The horror of sin continues as the object lesson continues and soon the peace of the Millennial Kingdom will display the final, stark, differentiation between God’s sovereign will and peace that reigns through obedience v. horror that reigns in disobedience. In the Kingdom, a thousand years is as is a day…God is NOT slow concerning His promises (2 Peter 3:8-9) and the faithful in Jesus WILL endure to the end (Matthew 24:13; Jude 1:24).