It's easier to manage 50 corruptions localized to their individual states, instead of the collusion of corruption at the federal level that is nationalized.
At least with the states, you have the self-interests of the other 49 states to balance the corruption of a runaway state. National corruption ends with weaponizing the arms of government against its people in order to protect the establishment.
At the very least, doing away with the elections will dry up the existing money spigots, such as McConnell's NRSC. He will have to rebuild a new power network to replace it, since it would be harder for McConnell to use national money to influence the state appointment in Mississippi or Alabama, like he's doing now.
-PJ
State corruption also can’t draw on an endless supply of deficit spending the way DC corruption does. (Although states like CA and IL are certainly trying!)