The money changers had legitimate business in the temple area. People would come to the temple to make an offering. However, the Roman coins had the image of Caesar on them and custom forbade a “graven image” in the temple area. The money changers were there to exchange a Roman coin for a “non-graven-image” Jewish coin and thus enable people to enter the temple and make their sacrifice. You can imagine that people wondered why Jesus was so upset to see this “money changing” going on. Apparently, the practice had lost its religious motivation and become a “cash cow” for the temple officials. The action of Jesus challenges us to see not merely what is happening but what is going on underneath the surface.