Because they all fit together somehow...
There truly is nothing new under the sun:
Aristotle warned: “Republics decline into democracies and democracies degenerate into despotisms.” The Federalist papers show us that the founding fathers understood this all too well. Just as the Roman Senate became more “democratic”, so to our own Senate changed from being indirectly elected to direct popular election in 1913. We were founded as a republic partly because democracies become weaker as they grow whereas republics can become stronger.