Those killed in the Donbas were because of the Russians.
Starting in 2012, your boi putin sent FSB and Spetsnaz to prop up his butt boi puppet Yanukovych. These FSB and Spetsnaz assets served with the Berkut secret police, and when Yanukovych fled to Russia in 2014, the Burkut went into the Donbas to whip up anti-Ukrainian sentiment.
Also in 2014, your boi Putin sent neo-nazi groups such as the Russian Imperial Movement/Russian Imperial Legion, and Rusich Group into eastern Ukraine to further whip up anti-Ukrainian sentiment. One of the founding members of Rusich Group Alexey Milchakov had a particular fondness of carving swastikas into dead Ukrainians in the Donbas region.
Those killed in the Donbas were ethnic Russians. Yanukovych was legitimately elected. Ukrainian Neo-Nazis are Banderites who celebrate their national hero, Stepan Bandera (1909-1959).
I cannot believe that you could be so confused about symbolism. It's called tagging to mark dead Ukrainians with swastikas to let their cohorts know that another neo-nazi fascist is dead. That's like a serial killer who murders prostitutes would tag them with the word whore.
It does not mean the killer was a neo-nazi, just the opposite.