Trump is right on this, but the analysis is as pointless as a guide to policy as correctly blaming the Treaty of Versailles for the German revanchism that brough Hitler to power once the Nazis were invading France. Yes, NATO expansion (and trampling Russian interests in the Balkans in the 1990s, and generally continuing to treat Russia as a definitional enemy even though post-Soviet Russia was not trying by force of arms and subversion to impose an unworkable and inhuman social and economic system -- Communism -- on the whole world) is behind Putin's revanchism of which the Ukraine invasion is the most brutal expression. But just as Hitler had to be opposed, the missteps of the victors in WWI notwithstanding, so Putin must be opposed, the missteps of the victors in WWIII (aka the Cold War) not withstanding.