The Ukrainian crisis can be traced back to the failure of a sensible deal between Ukraine and Russia regarding relinquishing some of Ukraine's sovereignty, which has led to Russia's consolidated political control and Putin's strategic mindset of regaining strength.
A story about a Ukrainian professor who stood up to a Russian mugger, in a situation that exemplifies the courage of the Ukrainian people against powerful forces.
The root cause of the war between Ukraine and Russia is the inability of Ukraine to make the sensible and rational deal with Russia, where they had to relinquish some of their sovereignty due to the latter's superior power.
Putin and Russia may view their control over energy as a way to reestablish strength and political control in response to the weakness Russia experienced after the fall of the Iron Curtain. This also allows them to undermine energy independence among other European nations.