Whereas the Babylonian harlot system of Revelation chapter 17 is the false, one-world religious system of the first half of the Tribulation, the Babylonian harlot system of chapter 18 is commercial in character.   "Materialistic Babylon" will be headed-up by the Antichrist.  He will bring about a (temporary) great economic boom for the nations, with a one-world monetary system, which will open the door to vast international trade and banking.  Men will gladly give their allegiance to the man-beast for having improved their financial portfolios because what they really worship is the money-beast.

Antichrist will devour ecumenical Babylon in the middle of the Tribulation, replacing the false religious system with his own religion: worship of him!  On the other hand, economical Babylon will come tumbling down "in one day" near the end of the Tribulation by the vial judgments that come directly from the Lord Himself.