> Russian involvement was widely reported
Sure. UFO sightings were widely reported to. Protip: not everything you read on the internet is true. There's a lot of bullshit out there, and a lot of people whose job depends on peddling bullshit and making people believe it. Some of them are Russians, but there are more than enough of them right in the US.
> it was not a post hoc rationalization for election defeat (in fact, the election defeat has, AFAICT, been blamed more frequently on Comey’s interference than Putin’s
It was blamed on anything except the actual performance of the candidates, as usual. Because taking responsibility is not something politicians do. Both Comey and Putin featured prominently.
> the Russian intervention and apparent active collaboration
Intervention in what? Collaboration with what? It is very symptomatic that object-less phrases are used to describe that - it creates nefarious aura without presenting a claim that can be verified. Russians "interfered" with what? They spent 100k or so on ads? It's peanuts, Hillary campaign spent 1bn+ overall - you are saying they couldn't beat Russian 100k with that? If that were true, that would be a sign on incompetence so gross that one has to wonder how they are putting on their shoes in the morning. However, it is baloney - Russian trolls had no traceable effect except show some stupid (and look it up, they are stupid) ads to a bunch of people.
Ah yes, there also is the question of stealing and publishing some emails (there were several cases) - some of which may or may not be obtained by Russians (public evidence so far is beyond shoddy and basically is "trust us, we know it's Russians" and can not be independently evaluated). But that part - and especially the part where Dems staunchly refused to give FBI access to their networks to investigate what exactly happened - somehow is not discussed that much. E.g. how comes their IT practices were so shoddy that they fell for a primitive phishing scam? What does it say about IT security of people who are supposed to handle the ultra-top-secret materials and still don't seem to give a damn about security? Etc. No, it's better to blame Putin and Twitter of course than discuss this.
> not because the losing party painted it as decisive.
Which they definitely did and continue to do so.