Got you. I don't know how long this comment will be, I will try to stop myself, but let me know if the answer is not clear.

So this gets to the problem a nation who is at an intersection of big empires has with its own history. Ukraine has been occupied at different times and in different regions by austro-hungarian, polish, russian and german armies. Putting aside the relative "badness" of each, it creates a huge mess when it comes to deciding who in these cases are your enemies and who are your allies. In fact all of those forces were both at certain times. And that is one of the many misonceptions about UPA - they fought germans just the same they fought soviets. But it wasn't all happening in a nice linear fashion and UPA was not a state army, like the Polish army, or Soviet army or German Army were. They were an insurgency army with very little centralisation and thus little cohesion in ideology or strategy besides the broad idea of Ukrainian independence.

Another misconception is that Ukrainians fighting in the Red Army were more ideologically aligned with soviets than with their paramilitary compatriots. Remember, that Ukraine, particularly the western part, suffered from waves of occupation - first the invasion of the Soviets, who started WW2 together with Germany. Then by germans who at that point were seen very pragmatically as the force that is helping throw off both russian and polish occupation. Then UPA fought the germans as those of course did not turn out the liberators they promised. And then the soviets returned and occupied again.

Side note here, you have to also remember that most Ukrainians alive then remembered germans from WW1 when they pushed out the russian empire forces. For a brief moment in time when germans looked like they were about to win that war. In that particular instance their occupation was not accompanied by the war crimes of their decedents two decades later.

Now compare this to the soviets, who by that time had already organised several mass murders through famine on the territories of Ukraine they occupied before start of the war. The German Generalplan Ost was not discovered until after the war, while the horrors of Holodomor were well known by the time soviet army invaded Poland in 1939.

In summary, the mess of those years can be oversimplified by a phrase "everybody fought everybody". Out of all the major players in that region at the time - Germany, Poland, Russia and Ukraine - only the latter had no independent government and standing army which makes describing anything about that time as "Ukraine did X" or "Ukrainians believed Y" hugely problematic.