Why did the riot occur in Ephesus in the bible Acts 19?

The Cult of Diana had their Temple in Ephesus. It was the center of their economy. When Paul, the Apostle came to town preaching the Gospel of Christ, people who were disillusioned by the useless goddess and ritual stopped buying the trinkets and idols that the silversmiths crafted.

A leader of the silversmiths named Demetrius, incited a riot against Paul and his companions, yelling "Great is Diana of the Ephesians" and much confusion ensued. As a Roman Province, they were all in danger of being scattered and/or killed by the Roman garrison for rioting until one of the city fathers was able to settle them down.

The account can be found in the book of Acts chapter 19.