Or it happens in exactly opposite way, ensures prolonged stalemate war and maximizes casualties. Sure it will weaken Russia a lot. However the price of humans lives in Ukraine would be devastating.
I'm sure that Russia would stop at Ukraine, and it would be to the benefit of the locals if Russia took over. I mean, appeasement of a sort always worked so far, right? Okay, the USSR screwed up historically several times in that area, among other things creating a system which managed to screw up massively enough to create a massive famine that took millions of lives on one of the most fertile lands in the world, purges, the whole delights of communism complete with a secret police thing... but I'm sure that was a fluke(s), and it's frankly a wonder that the Ukrainians aren't greeting the effective successors to the USSR with open arms! (sarcasm)
At the end of the day I'd say that it's up to the Ukrainians - the option for them to give up was always on the table. It seems clear to me that they keep on fighting despite the horrors inflicted upon them by Russia. As far as I'm concerned, that's heroism.
And, just saying, applying a similar mindset (don't support the defending side to "minimize loss of life") during WW2 could have shortened the war considerably, if with a
slightly different result.