Then they came to Jerusalem. And he entered the temple and began to drive out those who were selling and those who were buying in the temple, and he overturned the tables of the money-changers and the seats of those who sold doves; and he would not allow anyone to carry anything through the temple. He was teaching and saying, ‘Is it not written,“My house shall be called a house of prayer for all the nations”? But you have made it a den of robbers.’ (Mark 11: 15-17)

To allow a dispersed and increasingly urbanized population to participate in temple sacrifices it was possible to purchase sacrifical animals, such as doves, in the outer temple.

To purchase these holy items it was not proper to use blasphemous coin; for example, proclaiming the divinity of the Roman emperor. So there were those who - for a fee - would change secular coinage into temple coins.

Some have speculated Jesus was offended by a process that exploited the faith of the many for the economic advantage of a few. It is likely the priestly families benefited financially from this system.

Mark uses quotations from Isaiah 56:7 and Jeremiah 7:11 to tell us the purpose and message of Jesus. Yet another backstory. This was evidently the message that Jesus brought:

Thus says the Lord of hosts, the God of Israel: Amend your ways and your doings, and let me dwell with you in this place. Do not trust in these deceptive words: ‘This is the temple of the Lord, the temple of the Lord, the temple of the Lord.’ For if you truly amend your ways and your doings, if you truly act justly one with another, if you do not oppress the alien, the orphan, and the widow, or shed innocent blood in this place, and if you do not go after other gods to your own hurt, then I will dwell with you in this place, in the land that I gave of old to your ancestors for ever and ever. Here you are, trusting in deceptive words to no avail. Will you steal, murder, commit adultery, swear falsely, make offerings to Baal, and go after other gods that you have not known, and then come and stand before me in this house, which is called by my name, and say, ‘We are safe!’—only to go on doing all these abominations? Has this house, which is called by my name, become a den of robbers in your sight? (Jeremiah 7:3-11)

Above is Peception Deception by Amy Pilkington.