An Improper Consolidation

The Union was formed as a confederation of States that joined together voluntarily. It was the States that joined together, not the people.

The Founders saw the States as checks on the Federal government. They understood that the Federal government would attempt to assume more power than it was granted by the Constitution. So the Senate was devised in Article I, Section 3 in such a way as to give the State legislatures Senate-appointing powers. This made the Senators accountable to the States rather than special interests.