Another, even more important history lesson lies in Weimar Germany.
After the WWI, Germany was made a scapegoat, at the insistence of French. The conditions where the following:
ban of German submarines and airplanes
ban on German troops west of Rhine
ban on unification with Austria
ban on annexing Sudetenland
big swaths of land transferred to other countries (Poland, Austria, etc)
All of this imposed upon Germany even though Germans were lured to the negotiation table by the Americans promising there "would no losers". All of this led to rapid impoverishment of Germany and the rise of lunatic Hitler.
More recently, the historians labeled the 1990s Russia as a Weimar Russia. Even though Russia withdrew from East Europe unilaterally, the west has done nothing to help Russians deal with the turmoil following the transition to market economy and democratic institutions. When it came to loans, the west simply fleeced Russians. NATO also didn't waste time and move into Poland, and then former Soviet republics in the Baltics. NATO started the war in Yugoslavia and separated Kosovo from Serrbia despite Russian protests. All of this created great conditions for people to accept the autocratic Putin who nonetheless brought stability into Russians economy and politics, at the expense of rolling back the democracy and setting up a new police state.
At the same time comparing Putin with Hitler because of Sudetenland and Crimea is quite primitive. Hitler also advocated racial hatred and never made it a secret that he want to push the German nation to conquer Poland and Ukraine. With all its current problems, Russia is an multi-ethnic multi-cultural country with ethnic Russians constituting about 80% of overall populations. Even though, Putin used the nationalist rhetoric of helping Russians from abroad, the annexation of Crimea has broader goals. First, it's a demonstration of power, and a clear punishment of Ukraine for stepping out of line. Second, Putin just got another frozen conflict at the border, which means its unlikely Ukraine could join NATO any time soon.