To me this sounds more the the sort of thing foreigners tend to project on Eastern Europe (or whoever is outsider) then anything having anything to do with history or sociology.
The story is generally unlikely to be "general sentiment" of Russian soldiers. Among other things, there was enough mandatory political propaganda targeted at soldiers for them to not ask questions like this all that much, not loud.
> why would a country this rich invade a poor country like ours?
This question implies that soldiers assume the war was started because aggressor was poor and struggling, attacking out of no other choice. That gives quite a lot of benefit of doubt toward heavily demonized enemy in the war.
