Charles Beard argues that the constitution was written by a group of rich landholders who wanted to protect their property at the expense of the debtors and the poor farmers. The slaveholding, landed class, he believed, was not motivated by philosophy. Rather, they were motived by their own economic self interest. He believed that the radical democracy of the Revolution was an example of true Jeffersonian democracy, where power was in the hands of the common people. However after the Revolution, he argued, and freedom was won, the men in power wanted now to have laws designed to protect their wealth. He called the constitution a counter Revolution of bond holders (men who lent money to others and had a lot of money in banks and property) against the common people, the farmers and the debtors.
Beard was born well off but was a Progressive, and very liberal.
He would have argued that the stated truths, the principles outlined by John Locke and echoed by George Mason in the Virginia declaration and then discussed in the Declaration of Independence and then the Constitution, were not the true motivation of the framers. He believed that they were trying to protect their own wealth. The framers were powerful men of means. If you did not have property, you could not vote. Interestingly, George Washington rose from being a minor young relative of some property owners to a shrewd businessman and then marrying well and inheriting property, to become the richest man in the colonies. John Hancock made his fortune trading outside of the official British system and of course when the British imposed taxes on the men of commerce they did not like it. So yes, the framers were of course men of wealth and power. They certainly did some things, like allow slavery to continue, despite the obvious contradiction between their words and their ownership of other human beings. You probably also know of Jefferson's personal history with Sally Hemings.
Whatever the personal motivations of the framers, Charles' Beard's interpretation is interesting but clearly a one sided view from the Progressive political camp. One could argue that although the framers did want to protect their money, the system created here in America and codified in the Constitution gives everyone a chance to succeed.
When you answer this question, please review your book for discussions of Progressivism so that you will see where Mr Beard was coming from.