They didn't really care what happened to _anybody_, not just Ukrainians. Ukrainians (as well as about 30% of Russians) just happened to live in that particular location. The plume made it all the way to the Nordics and Germany, and I, as a kid, had to take iodine tablets in Russia, even though officially everything was "under control" for a few days. Then the narrative shifted to showing the heroism of the "liquidators", never fully acknowledging how dangerous any of this really was.