I am well aware that you're "just asking questions," ho ho, but this question actually does have a specific and interesting answer:

https://en.wikipedia.org/wiki/Svoboda_(political_party)

The TL;DR is this: The closest thing Ukraine has to a neo-Nazi party, which is honestly pretty close to one, had some pretty strong legitimate support before the 2014 revolution. Basically, "anyone but Russia" was the thinking of a lot of people, and Svoboda showed a willingness to do things like get in fistfights with pro-Russian politicians which got them some credibility and support. Basically, the same type of faux-populist "back to greatness, we'll fight for you" appeal that Trump was able to ride in the US, and it did legitimately work. They got 10% of the vote in 2012, and they won majorities in some places.

In the aftermath of 2014, once there were populist candidates who were not eager Putin's-knob-slobberers available (and, also, when their Nazi tendencies were starting to become a lot more obvious), their support cratered like a poorly designed submersible. In the 2019 elections, they Voltroned up with all the other fascist parties, hoping to merge support and at least meet the 5% threshold to keep some kind of representation in government, the aggregated blob still just got 2%, surely only that high because it really wasn't that long ago when they were seen as a legitimate and helpful party.

TL;DRTL;DR: If Russian wanted to denazify Ukraine, they could have just done another Euromaidan, that was by far the most effective denazification event that has happened for decades in Ukraine.