It doesn't really matter what Russia sees as a vital strategic interest if they have no money to pay soldiers and purchase weapons, no food to feed their soldiers, and no water to drink.
On a related note, Russia really does not have very many modern aircraft and tanks. They have ~150 T-80BVMs, ~100 T-90Ms, (compared to ~1800 M1A2 SEPV2s and M1A2Cs) and maybe 150 KA-52s (Compared to ~800 AH-64s and 90 AH-1Zs). They've lost at least one T-80BVM and at least one KA-52 absolutely confirmed on videos in this thread. Those losses are simply unsustainable on Russia's paltry and dwindling resource pile.
People in this thread screaming that Ukraine is lost and Ruskies are on the verge of capturing Kyiv need to reevaluate their retardation.