Russia is currently fighting a war is with a client regime that US installed in Ukraine after overthrowing the democratically elected government in 2014. I generally agree with the reasoning for why Russia decided to start a preventative the war that Mearsheimer gives here.

While Russia has a reactionary capitalist regime, it is acting as a bulwark fighting against US global hegemony right now. NATO has been forced to devote practically all of its resources to the proxy war and this created room for the Global South to finally start shaking off western hegemony. We are seeing a major global realignment happening with countries moving off the dollar and BRICS rapidly expanding.

The war has also derailed US plans for containment of China, and it's clear that China is taking advantage of the additional time that Russia bought it. I expect that by the end of the war we will likely see the reverse moment of when USSR collapsed, and US led capitalist world order became dominant. This time around, it will be the capitalist order that crashes, and it will be replaced by socialist one led by China.