It seems like we have much smarter people in the House. It’s probably a simple matter of the electorate. Statewide, the Senate races have to appeal to a broader amount of people. So the message and the candidates get dumbed down. The higher turnout you get, the more the big money knows that it has to dumb down its message to get its support up, since in any large population the dumb people outnumber the smart ones.
With individual House districts, they are smaller so you will find districts with a higher average intelligence that can elect a more intelligent representative. You’ll also find Charlie Rangell’s district.
This also explains why one of our dumbest elected officials is in the White House. A nationwide election is the most dumbed down election of all.