It makes sense from the perspective of Putin. His country lost the Cold War, modern day Russia is in a compromised position because of it, his country is dying (literally) and he has a limited time to make one last stand. Russia's current borders do not plug all the access points like the Soviet Union's did. Ukraine is one of those access points. I think he knows that NATO would never actually invade Russia, but this is also about keeping NATO influence out of territory he considers to be in his sphere of influence. Putin does not want to be a bit player in a show that someone else runs. He wants to run his own show.
I am fairly young myself, but also a history nerd and what I've found is that the world generally tends towards conflict and disorder. The postwar period and particularly the post-Cold War period are more anomalies rather than the way things normally are. From the Middle Ages until 1945, Europeans routinely fought major wars that directly involved the major powers in direct conflict with one another. The last two conflicts they fought ended up involving most of the industrialized world.
After they all blew themselves up during WWII, the only major power whose industrial base and navy survived the war intact (ours) came up with some new rules of the game, and the world has been running according to those rules ever since. However, the Cold War is over, and the US has less of a desire to continue that program than we used to. IMO, the world in some ways is reverting to the way it normally is; we just aren't used to it because we've lived during this unique time period.
