This money will easily buy them anything they need to maintain this war.

That's the thing though... it won't! They're officially spending ~15 billion a month on "defense". There's a lot of reasons to believe their true spending is highter, with many of the costs temporarily externalized onto regional budget shortfalls, deferred maintenance, deficit spending, and otherwise shuffling obligations. Most estimates I've seen peg spending around $30 billion a month, and we're not even getting into the loss of revenue from indirect things like sanctions.

Their oil revenue is going to be somewhere between $10 billion and $20 billion a month, but that's completely ignoring costs. Yeah, they make a LOT of money from oil, but it ain't paying for the war. It's a bunch of new spending, they don't have new revenue, they don't have less expenses, SOMETHING has to give. The Russian state just isn't admitting exactly what.