But what Russians expected can be inferred from what they did - their initial Kyiv offensive, Hostomel landing, it's a clear attempt at a decapitation strike. It's actually a carbon copy of the 1968 invasion of Czechoslovakia which fell without a fight which is apparently what Russians expected here as well.
But in this case I'd emphasize that even if that was successful they would have known it would be far from the end of the war. The 'nationalist units' and at least some regular forces would resist, the West would predictably back them endlessly (and probably bring in proxy forces) and the most likely scenario (absent a quick settlement) would be something like Afghanistan 2.0.
While a great talking point in Russian circles, nationalist units did not represent a significant chunk of Ukrainian forces in 2022. They played a role in the power vacuum of 2014, but not by 2022.
Regular forces were concentrated in the east. If Russia took Kyiv, they'd effectively cut off any supply routes from the West. The resistance would be futile. Remember again how forces in Crimea resisted forever?
> and probably bring in proxy forces
Could you expand on this? Where, who ... how?
> and the most likely scenario (absent a quick settlement) would be something like Afghanistan 2.0.
Most likely based on what? Where do all these fighters hide? Are the Ukrainian plains as good for hiding and launching covert attacks as Afghanistan caves?
After that claim was demonstrated to be clearly idiotic, the propaganda machine then began subtly (and then not so subtly) suggesting it was actually Russia that was making such claims.
But that was always plainly absurd. The last normal war Russia had was against Chechnya, another country that was tiny and practically unequipped relative to Ukraine, yet that war lasted a decade and had tens of thousands of deaths with a huge culture of great music [2] perpetually reminding people how brutal that war truly was.
You won't find a single source from a Russian political/military leader saying it'd be short, because they all knew it wouldn't be if there wasn't a quick agreement reached. The one quote people were able to find was from some television personality in some segment. But I hope Russia(ns) aren't citing e.g. Rachel Maddow to get insight into American positions on issues !
[1] - https://www.foxnews.com/politics/mark-milley-ukraine-war-pre...
[2] - https://www.youtube.com/watch?v=8e5GDbkS3Gw