Why must all these things be consummated in the plan of God?
All these things must be consummated so Christ can bring everyone—believers and the angelic hosts—to the fullest understanding of who He is. The sequence includes the tribulation’s end, His Kingdom, Israel’s covenant promises, His rule over all the earth, and His final defeat of death.
Les explains that after the consummation of the tribulation, the King comes and sets up His Kingdom. Israel will finally enjoy all those covenant promises, including territory clear out to the Euphrates River, not desert sand but like the Garden of Eden. All the earth will come under Christ’s rule and reign. After He has shown His authority and power, He must defeat the final enemy, death. Les says all these things have to be consummated in order for Christ to bring to the epitome of understanding—even of all believers and the angelic hosts—of who He is. The context also notes the devil, beast, and false prophet are cast into the lake of fire and tormented forever, with the later judgment of the lost and their doom.
For he must reign, till he hath put all enemies under his feet.