What I found ironic that both people in the Far Right and Far Left (especially the ones espousing pro-Russian / Novorossiya rhetoric) uses the fact that there were many instances where the Wehrmacht was welcomed and supported by the Ukrainians (at the beginning at least) to support their respective arguments which is:
But from what I've read so far seems to suggest that such enthusiasm were only found in Western Ukraine. Some of the most prominent collaborationist units were based in the West (e.g SS Division "Galizien"). Is this true? If so, why such discrepancies compared to other region of Ukraine?
The Nazis received a warmer welcome in the Westernmost parts of the Soviet Union for a few reasons. First and foremost, the regions had only been part of the Soviet Union for at most less than 2 years and as a result had little attachment to the new regime. Second, the Soviet occupation eliminated all but the most radical political parties which existed in the interwar Baltics and Western Ukraine. Thirdly, Soviet policies such as collectivization were implemented swiftly and ruthlessly, even more so than they were in the Soviet Union itself, alienating even potentially sympathetic groups. So the regions were a powderkeg in 1941 where people believed that they could revolt against Soviet power and then convince the Nazis to grant them independence - a foolish gamble in retrospect, but at the time they had few options. However, for the collaboration of the "average" person we shouldn't put too much weight on prewar identities. Many loyal communist party members collaborated during the war out of fear or self-preservation, and resistance in Nazi-controlled areas was limited until the Red Army began to push westward in 1943. Even in Belarus and Northwestern Russia, known for their partisan resistance in popular mythology, collaboration was widespread.
Sources:
Bernstein, Seth, "Rural Russia on the Edges of Authority: Bezvlastie in Wartime Riazan', November-December 1941"
Enstad, Johannes D., Soviet Russians under Nazi Occupation: Fragile Loyalties in World War II
Exeler, Franziska, "Reckoning with Occupation. Soviet Power, Local Communities, and the Ghosts of Wartime Behavior in Post-1944 Belorussia"
Melnyk, Oleksander, "Historical Politics, Legitimacy Contests, and the (Re)-Construction of Political Communities in Ukraine during the Second World War"
Statiev, Alexander, The Soviet Counterinsurgency in the Western Borderlands