What does Revelation 18:9 mean?

According to this passage the kings of the earth weep and wail over Babylon's collapse. Unlike chapter 17, where "Babylon" was a reference to a form of false religion, this "Babylon" describes politics and economics. The reference to "kings of the earth" suggests rulers worldwide: kings, presidents, prime ministers, and dictators. So far as Revelation is concerned, the demise of "religious Babylon" wasn't mourned. Here, however, the fall of this economic or political superpower is a source of grief.

The term "sexual immorality" implies certain physical sins, but it's also a common metaphor in Scripture for the sin of idolatry. The actual city and culture of Babylon, historically, was deeply rooted in the worship of false gods. As it applies to the end times, this may refer to the idolatrous act of worshiping the beast. Revelation 13 relates that the False Prophet in Jerusalem set up an image for the beast and demanded everyone to worship the image.

These political rulers found it financially advantageous to cooperate with Babylon. Babylon's ruin would cause them to experience their own financial ruin. When the stock market in the United States of America crashed in 1929, wealthy investors lost their fortunes. Overwhelmed with their losses, many took their own lives. Perhaps, the fall of Babylon will produce even worse results. The earthly kings' tears flow profusely as they watch smoke rise from Babylon's burning. The drifting smoke might be seen directly in nearby cities, but modern technology can broadcast the disaster worldwide.