John Mearsheimer is an internationally renowned geopolitics analyst known for his criticism of the US-american foreign policy establishment. He has written the book "The Israel Lobby and U.S. Foreign Policy" (2007) as well as "Why leaders Lie: The Truth About Lying in International Politics" (2011). In recent years, he has taken the minority view that the Ukraine crisis is the Wests fault, which he had put into words in an article published in Foreign Affairs back in 2014 when the crisis initially broke out. While Mearsheimer himself states that his views are not mainstream, he is still a popular guest on panels to debate the conventional wisdom of conflicts such as the Ukraine crisis. He states that while Ukraine is not a de jure member of NATO, Ukraine has been integrated into the framework as a de facto member. This would be considered a threat to Russia's national interest, which is why it came to no surprise that the Russian leader would go to great length to wreck Ukraine, to avoid it becoming a western bulwark on Russia's border.
Mearsheimer goes into detail how this crisis started back in 2008 at the Bucharest NATO summit, where both Georgia and Ukraine were invited to become part of the military alliance. He also explains why nuclear threat is on the table and why we need to shut this war down as fast as we can.