Our founding fathers understood that democracies always like cancer always metastasize and lead to the death of destruction of the host. The Constitution was written to protect the people from the tyranny of the majority in a democracy.
The understood that having a house to represent the people and another house to represent the states would guarantee that both the large states and the small states would have a voice, If the Virginia Plan which would have created two houses representing the people and no house to represent the states had been accept, the large states would dominate the small states.
Before 1965 the state legislatures had a house to represent the people and a second house to represent the counties. This arrangement prevented the large counties from dominating the small counties. With the majority in the state assemblies, the large counties could pass virtually any legislation they wanted, but without the support of the rural counties their legislation would be blocked. This was one of the fundamental checks and balances that prevented the tyranny of the majority,