It's hard to say why it happened, though I'd guess it was in part that the selection of Senators by state legislatures made them more beholden to those bodies t

It's hard to say why it happened, though I'd guess it was in part that the selection of Senators by state legislatures made them more beholden to those bodies than the people of the state or the country. Since state legislatures of the time were notoriously corrupt, they regularly sold off Senatorial seats and used their Senators as puppets for their agenda. State Legislatures of the time were also vastly overrepresented by rural districts, which may have played into Senators having more indifference to national interests over provincial ones.