The direct election of Senators considerably changed the Senate. The Senate’s job was to represent the interests of the individual states, the House was to represent the people. That’s why the Senate has treaty powers — as the United States (emphasis on the plural of states) are/were each sovereign entities and the Senate thusly had to approve of any treaty that woukd effectively bind states to an international agreement.
Direct election of senators changed that because the senators no long answer to the state governments but to the population of the state directly.