its another country that has suffered from moving borders, Lvov used to be in Poland for example.
the issue is more than there are a large group of "ethnic" russians in the eastern half which was heavily involved with industry and oil and gas (hence the gas pipeline from Yamal peninsula headed south to link up before heading to europe). Ukraine also has a vocal ultra nationalist movement and naturally makes the "Russian" Ukrainians nervous. In most places it might be considered racist but because the minority are the Russians (and the bad guys) it makes it ok ??
I was there in 1997, couple hours drive north of Donetsk, lot of Russian speakers, often feeling "lost" even then. Their parents or grandparents had moved there back in the good old CCCP days, they were ethnic russians but had never lived anywhere else than Ukraine. Partition was debated even then.
Not dissimilar to the Baltics back in 1990s where the "almost minority" passed various "anti-russian" laws almost to punish those with links to the former occupying power, things like not getting a vote unless pass a nationality test that had to be taken in Estonian for example.