They are random strangers to the people gaining pleasure from watching their preferred snuff videos. Those people must be delighted to have found a way to "justify" their pleasures.
The same combination of dehumanisation and pleasure in the suffering and death of others is what's found in the most savage of war criminals. The biggest difference between those people and the people they're using as "justification" is circumstances. I've no doubt they'd be raping and torturing and murdering if they were in a war and could get away with it. Or at least that they'd want to do so. The mentality is identical.
Many of the Russians invading Ukraine don't really know what's happening or what has happened. They don't have access to information other than the propaganda they've been fed. They've been told they're defending their country from an attack by NATO Nazis. That they're liberators, not conquerors. Also, if they express any dissent they'll probably have an "accident". In modern Russia, a person can fall out of a window when they're in a tent on the ground. Or maybe the whole "accident" thing will be dispensed with and they'll be beaten to death with a hammer. Openly. On video. For some people to watch with joy.
Many of the Russians invading Ukraine are conscripts. Stripped of their freedom. Enslaved. Forced to fight in a war not of their choosing. Probably to live in vile conditions for a short while and then die because their masters don't even care enough to equip them for survival. While some random strangers to them gain pleasure from their deaths.
Most importantly of all, gaining pleasure from watching snuff videos is about the watcher, not the watched. Killing people is sometimes justified. But it should never be a source of joy. That's totally messed up, just plain wrong in the head.