I watched that lecture but I still don't understand the situation. He explains that since the fall of the Soviet Union, Russia made very clear that they did not want NATO to expand beyond Germany. And yet NATO did expand into Poland and the former Soviet states Lithuania, Latvia and Estonia etc. So why is Putin responding
now when he already ensured Ukraine wouldn't join NATO in 2014 by invading the country's western region?
Secondly the lecture doesn't explain why Russia is so concerned about having a NATO member on their border. The treaty is a defensive one, not offensive. I don't think the lecture does a good job to help westerners understand the way in which the east mistrusts the west.