Russia has a history of fighting and winning against Nazis just like the Azov battalion and those who we knew during WW2. Russia has made clear they only want those disputed areas to be independent, the ones marked by the Minsk treaties, you know, the ones Ukraine didn't follow. Ukraine will lose, it's just a matter of seeing when. They're at a strong enough position now though, they could take minimal losses in this. Further, knowledge of the chemical weapons labs (also illegal internationally) that could have been used on the people in Donbas had they been allowed to continue, was probably the catalyst for action.

Nonetheless, leaving Russia out of it, the people of the Donbas region have asked the UN for them to become independent multiple times, independent of Russian support. The US State Department also documented many human right violations on these people from Ukraine's government . Their wish should be granted as the most recent votes show.

This document is from the State Department website. It makes clear what kind of human rights violations have happened there. I will never support Nazis and if you look at US News reports from even just 4 years ago, its' clear the country they are in is Ukraine.

https://www.state.gov/wp-content/uploads/2020/03/UKRAINE-2019-HUMAN-RIGHTS-REPORT.pdf