It's one of the key goals of Russian information warfare: to create a feeling that you can't tell truth apart from fiction, and to force you into apathy and paralyze you, so you become unable to act and protect your interests. Russians are among the largest pushers of conspiracy theories from Covid to QAnon, and have been for a very long time, because it is cheap and very effective way to divide free societies into infighting groups. NYC station chief of Russian foreign intelligence used to visit public libraries to post conspiracy theories on Geocities in 1990s -- that's how important it was and remains.
They flood all available channels with utter nonsense to make people turn their brains off. Just today a general and the spokesperson for Russians Ministry of Defense tried to justify the war by saying that the United States was training migratory birds in secret Ukrainian laboratories to carry dangerous pathogens into Russia: https://redd.it/tb6sn8 Antivaxx groups have already switched to parroting such crap, because many of them are seeded by Russia.
By the way, Mearsheimer is an idiot and nobody takes him seriously in Eastern Europe. You might as well read books by Nazis explaining why Germans had the right to Lebensraum in the East. Instead of precompiled knowledge provided by TV talking heads or authoritative-appearing "experts", I recommend building up knowledge from basic building blocks. Start by reading general histories of the regions you are interested in to understand historic difficulties that people in those places have faced over the past several centuries and what their current goals and motivations are. Then you don't need Mearsheimers to tell you what's going on, you can derive it from your knowledge. This applies to everything else too. If you know a thing or two about basic statistics, then you're much less likely to fall for bullshit narratives like Covid conspiracy theories from people who look trustworthy. Knowledge is power.