God’s Sequitur, and/or Alternative, “Second Coming” & Millennial Geo-Resetting Event (=Rev 3:3; 14:1-5ff; 20:1-4ff)
In Rev 19:1-10, the results of the effectuated judgement on Babylon are related, as well as an indicative time as to when, -in actually the plagues, contrary to wished expectations (Rev 22:11). As seen in the Revelation Charting here, Rev 19:1-10 serves as an anticipative, introductory vision passage which sets the context of what takes place in the rest of that prophetic segment.
Rev 19:1 - After these things I heard something like a loud voice of a great multitude in heaven, saying, "Hallelujah! Salvation and glory and power belong to our God;
great multitude in heaven - This great multitude are those who, through this Loud Cry Call out of Babylon have responded to this work of the priorly sealed 144,000 (Rev 7:9-17). Indeed many of the same themes expressed there are restated here in Rev 19:1-10.