They aren’t going to win. Their economy started with noticeable issues and has since been obliterated. Aggression wars against a weak opponent are remarkably expensive and Ukraine has received a significant amount of support (I’d estimate around 20b so far) whereas the ruble and Russian markets (bond, equity, and a large portion of export/import) have been nuked. They are running on fumes in a war that is projected to run for quite some time.