Perhaps because Russia doesn't stand for other countries to sow and support separatist groups in Russia, as they do in other countries.
We've gone over this; "well-documented"
by whom, in a world in which deviating from the left evokes "Nazi!"? I find PLENTY of allusion to that but don't find it compelling evidence.
I gave a brief history of OUN, including their collaboration with Germany to rid the country of Poles, Russians, etc., who had ruled and abused them. How they saw Germany as liberators which lasted about one month until Bandera was tossed into the clink and then Sachsenhausen concentration camp until Sept. 1944. Bandera didn't hate Russia because he was a devotee of Nazism, but of Ukraine; I don't ***** blame him.
It's a girthy topic, but essentially did the nationalists kill Russians and Poles because Ukrainians were Nazis? Of course not. To the degree they were antisemitic, it appears based in that Jews supported the Muscovite rule, and not an independent Ukraine. The Germans concluded OUN and UPA (Ukrainian Insurgent Army begat by OUN) were indifferent to Jews, and would alternately kill, shelter, or employ them as best served nationalist aims.
Wikipedia is an easily accessible, leftist org. I expect them to call OUN, Bandera, UPA, Azov 'Nazis' and imply the Ukrainian government has a 'Nazi problem' and they oblige on all counts. But, even their pages don't support the Nazi allusions they make. Like science, truth isn't a democracy that a mob of implication can overwhelm by sheer numbers. Here's a handful I urge people to read for themselves, my dog isn't fighting:
Stepan Bandera - Wikipedia
Organization of Ukrainian Nationalists - Wikipedia
Azov Battalion - Wikipedia