The state government is a consolidated view of the people in that state. That doesn't mean that everybody in the state agrees. But, it does mean that there are some settled issues at the state level. A state's senators should be representing those settled views.
Senators did represent the people but once removed. The people can be swayed by a smooth talker or a pretty face. The state legislature selecting senators ensured that senators represented the collective wishes of the state and reinforced state sovereignty by giving the state government a voice in congress. The Senate acted as a check on the people's whims represented in the House.
Federalists 62, 63, 64, 65, 66, 75, and 76 address the Senate but the reason for the Senate is summarized at https://www.senate.gov/about/origins-foundations/idea-of-the....
Unless a Constitution describing a large government is ratified I will stick to my belief that a large portion of the government is unconstitutional and unnecessary. The Constitution explicitly says that the only powers the federal government has are what is described in the Constitution. Anything beyond that shouldn't exist at the federal level.
A small federal government ensures that what the people of one state want has absolutely zero effect on any other state. It ensures that the people that live closest to each other are deciding the rules they live by. That makes for a happier populous as the people feel they actually have a say in how their lives are governed. A large central government is costly, ineffective and overbearing.
