Explain a key reason why we have delegated legislation.
The Founding Fathers, and particularly the Federalists, feared anarchy as much as tyranny, and believed that direct democracy would be tantamount to mob rule. They also believed that most of the men who comprised the population of the colonies at the time of the drafting of the constitution were poorly educated and unfit to make wise governing decisions. This is why the Founders, who were by and large well educated and wealthy, wrote about the "tyranny of the majority." These prominent men of their day did not trust the majority of the population to rule wisely, but instead feared their lack of sophistication and tendency to act based on their emotions instead of their intellect.
Therefore, the Framers chose to create a representative democracy (a republic) which would purposefully dilute and moderate the will of the people, by encouraging ordinary men with voting rights to elect well educated, land-owning, respected men within their communities as their representatives. These representatives would in turn make laws that reflected the desires of their constituents without sowing chaos or confusion, and without tending towards extremes. If you read the Federalist Papers, you will hear this concern echoed time and time again.
Remember that according to the Constitution, only members of the House of Representatives would be elected directly by the people. In order to further check to "will of the people," the Founders made sure that members of the Senate, "the Upper House of Legislature," were not directly elected, but chosen by party leaders. This did not change until 1917 and the 17th Amendment. Moreover, it is the Senate, not the House, which confirms Presidential nominees to the cabinet and courts. This was not an accident. The Founders did not want "ordinary citizens" to influence who would be seated on the courts or who would comprise a President's inner circle of advisors. Similarly, the Founders created the Electoral College to dilute the public's ability to elect a demagogue as President. All of these steps were aimed at controlling the passions of "ordinary voters," and making sure that the will of the people was carried out in a sober, deliberate fashion.