As I understand it, the Constitution was designed to provide several layers of indirection when selecting federal officials. In the original design before subsequent amendment, voters only directly elected their congress person and their state legislatures. US Senators were behind one layer of indirection, being selected by state legislatures who were selected by popular vote. The Presidency was behind two layers of indirection: selected by vote of electors, who were selected by state legislatures, who were selected by popular vote. Finally, the Justices of the Supreme Court sit behind multiple layers of indirection: nominated by a President who is selected by electors, and confirmed by Senators, with both electors and Senators selected by state legislatures, who in turn were selected by popular vote. The idea was that the greater individual role an office had in preserving the constitutional system, the more insulated they were from the direct influence of unruly voters, and the more institutional support was necessary to assume office.

I always thought this system was overly complex and did not adequately respect the views of the people, but now in the year of Trump, it increasingly seems like a wise idea lol.