The claim of butchery and mass murder is being assumed and then willful intention ascribed on what basis? I don't understand the casual assertion of monstrous crimes.
Several reasons.
A -- This entire thing was easily averted if Zelensky had simply 1) agreed to abide by the Minsk accords that Ukraine had already agreed to and 2) Zelensky had promised not to join NATO, something to which Ukraine and NATO had long agreed to. But Zelensky refused both.
B -- Fighting Russia was hopeless to being with. Ukraine simply can't win, so whatever goals they might have to recapture "their" lost territory are exercises in futility, and therefore a needless loss of Ukrainian life.
C -- Recent counter-offensive was utterly hopeless, and wave after wave of Ukrainian forces were going into a meat grinder and on ѕυιcιdє missions. There are videos of some Ukrainian soldiers complaining about what Zelensky was hoping to accomplish other than the depopulation of Ukraine.
D -- Soros, who propped up Zelensky (and his predecessor in 2014) has long stated that the goal was to build up Ukraine to use as a "torpedo" against Russia (torpedos are destroyed when they hit their target). Merkel admitted that signing the Minsk accords were merely a tactic to buy time to arm Ukraine to go after Russia. This entire thing was instigated by the West / NATO / US and they're using the Ukrainians as pawns in their game, caring nothing for the loss of life.
Zelensky is a Jew and doesn't care a rat's behind about the Ukrainian people, but is doing the bidding of his Jew paymasters and puppetmasters.