Why were senators originally chosen by state legislators?

Senators were to be chosen by state legislatures, because many of the Framers of the US Constitution did not trust the general populace of the country to vote for the right men to be Senators. Once the decision to have two houses of Congress in the form of a Senate and House of Representatives had been made, the idea was that the Senate would be the wiser, more responsible of the two Houses. The Senate was seen in much the same way as the British House of Lords is in comparison to the British House of Commons. The Framers debated four methods of choosing the Senators: by the House of Rpresentatives; by the national executive (President); by the state legislatures; or by the general public. They settled on the state legislatures because they felt each state's Senators should be chosen by the states themselves but that the Senate was too important to be left to the general public. In fact, several framers thought the general public was not much better than a mob.