Russia - threadbanned users in OP

Delusional perhaps but not without grounding. The Russian state is a total black box and it's impossible to predict its future with certainty sure: but it also can't be wide of the mark to speculate that this war - as wars have done with Russia before, time and time again - is gonna be the catalyst for collapse, regime change - or both. The clock is ticking here IMO. Russia is kinda pulling a Weekend at Bernie's at this stage: the state's functionally dead across a host of metrics, it's just being propped up by a cartel headed by a now proven delusional wannabe Tsar itching to reform "historical Russia". Coups happen fast, and I don't think any of us will see it coming - least of all Putin. He has definitely stamped out all opposition but he may want to keep an eye on his military bigwigs for one.

Kyiv is fighting for its life and will do so I suspect to the bitter end; pure spite and gumption has turned this 3 day war into a 2+ year one and by and large that's on the Ukrainians will to persist. Even if Russian tanks rolled into Kyiv tomorrow? They're not gonna go anywhere cos then the Guerilla war / insurgency will begin and so Russians will keep dying - albeit not quite on an industrial scale.

"All Ukraine has to do" is hang on long enough 'til Russia's ability to prosecute the war runs out and I'm not sure that's as crazy or far off as you might think. That assertion isn't wrong but it doesn't factor in the reality that one side has a greater will to win than the other - a will that'll extend past the capital falling. Whereas Russia? Can it just keep going and going?

North Korea has and will endure because it put the legwork into intentionally becoming a feudal, utterly insular state. I don't think there's a single comparable nation on earth when it comes to the Pyongyang dynasty. While the difference with your other examples is neither state put an inordinate amount of its resources into a war it cannot win, yet has already lost hundreds of thousands of lives, and as many have fled the country - in a country that was already suffering crazy demographic problems before the war started. That centre can't hold forever.

It's easy to forget but Russia was once a grubby country everyone looked the other way for, because it was the source of our gas, finances, World Cups and sundry other little tendrils that had ensured we pretended Putin was a normal world leader. They were as bad at whitewashing as the Saudis continue to be. Then he miscalculated that apathy and ordered his tanks towards Kyiv.

I'll say one thing you're way off about: ain't no chance Russia's gonna replace Putin with someone better - in fact I maintain a degree of worry it's gonna be someone worse. Dissent and legitimate political rivals are effectively dead and gone now, so what's left? It's entirely possible a smarting Russia ethno-nationalist will take over and push the country into a further antagonistic stance.