This is a horrifying result no matter how you slice it.
Something has gone horribly wrong in American politics, and I don't think it's going to get fixed any time soon.
I seem to recall an incident in 2006 where Conrad Burns attacked a group of out of state firefighters for "not doing enough" to help with the wildfires in the state.
Many thought it contributed to his loss, perhaps it did considering how close it was. But, Burns was trailing by 20 point and IIRC, subsequent polls to that incident showed Burns gaining ground.
I tend to think you are right to some extent, especially with regards to Montana as this is the second time that such unacceptable behavior, seemingly didn't play out the way it would have expected.
Or perhaps it is just coincidence.