The best explanation for why the Framers created a bicameral Congress is:
The bicameral Congress was created due to a compromise following a dispute over state representation.
This refers to the Great Compromise (or Connecticut Compromise) during the Constitutional Convention of 1787, which resolved the conflict between states with large populations wanting representation based on population and smaller states wanting equal representation. This led to the establishment of a two-house legislature, with the House of Representatives based on population and the Senate providing equal representation for each state.