Communism is primarily about economics:
Communism - Wikipedia
Putin said that Russia is a 'Market Economy'. Russia/China is a mixed economy like Europe & US. where gov't is mixed with the market.
The chief difference is the nature of the mixture, which is different from country to country.
Russia is traditionally obsessed with security as it's the largest country in the world, has to govern vast territories, and is pretty easy to invade. Putin's Red line was in 2014 when they were losing their influence in Ukraine. They were very afraid that Ukraine will turn into another US Army base. Then the US re-militarized Ukraine, provided training advisors, and re-activated the Soviet arsenal prior to 2022 invasion.
Ukraine was once a very important part of Russian security, the whole territory was highly weaponized and industrialized. IMHO the centralized ethnic argument is just a cover for their (unspoken) issues with NATO penetration into the East.
Without knowing too much about Russia internally my first guess is that they are afraid not only of the US-NATO military colonizing Ukraine but also of how the West uses military occupation to infiltrate countries economically, culturally, and politically primarily with multi-national corporations and influencing political processes. This would influence the economy of Russia just by association and threaten their ruling class (oligarchs, government bureaucracy, FSB, military etc)
The Biden family also has economic interests in Ukraine, like other US politicians and financiers.