There are two things that people all over the world tend to put their trust in: religion and wealth. The last two messages from the book of Revelation addressed why people follow religion and the source of the many different religions they follow. We saw what the ultimate end of those religions are in Revelation 17. Now, in chapter 18, we see the fall of the second object of people's trust and passion: wealth.
Wealth in itself is not evil, but wealth as a passion, as a goal, is. In fact, God calls greed equal to idolatry and here in Revelation 18, we see their end is the same.