The concern isn’t about the consequences faced by Russia, but the impact on the rest of the world. Like, if Russia were to collapse, I think most would agree that Egyptians don’t deserve to find out what suddenly not having $1.7 billion in wheat would mean, right? I don’t think anyone has any idea what that would mean for, say, Tajikistan and other post-Soviet states with economies closely tied to Russia. Collapse would be chaos and it wouldn’t stay confined within Russia’s borders.
And, again, I don’t think that justifies preventing Russia from losing. There are worse concerns for Russia winning. And the idea that Russia neither winning nor losing could be a sustainable final state is probably a fantasy.