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) that settled disputes between states with larger populations, which wanted representation based on population, and smaller states, which wanted equal representation. This led to the establishment of two chambers: the House of Representatives, with representation based on population, and the Senate, with equal representation for each state.