They have been around a long time. Lots of stories of these guys from back in 2014, but there was an underground dating back to WW2.
It goes back to Stalin - well, earlier, but Stalin was the worst of it. The Ukes were devastated by Stalin (see “Harvest f Sorrow”, Robert Conquest), to the point that many took to cannibalism. So they developed a lasting hate for the Soviets and the Russians. So much so that they sided with the Nazis when they showed up. Some of that is still around today, as you see.
Lots of reaping of whirlwinds and chickens coming home to roost and sins of the fathers and so on all over the place.
The biggest mistake in hindsight was not having a formal conference, like Helsinki in 1975, to approve the borders of the new countries after the breakup of the Soviet Union. Would have saved us a lot of trouble.