Bottom line:
If the Rs that lost their seats had pleased their constituesnts, they would still be in office. You just can't break it down any more than that. That's how it works.
The base came out for the last election and voted accordingly. Several seats were lost with Dems running to the RIGHT of their R opponents. Blame the voters all you want. It's like blaming the customers when a store does poor business.
It's also more than a little like cutting off your nose to spite your face, then complaining because now you have no nose. Remember: if you don't like what the 'Rats are doing to the country, you can thank yourself as one of those who put them there.