That is indeed the case, it's important to keep in mind that Ukraine was created by USSR out of parts of Russia, Poland, Hungary, and Romania. I highly recommend watching a lecture that Mearsheimer gave back in 2015 to get a bit of background on the subject. Mearsheimer is certainly not pro Russian in any sense, and he gives an objective analysis of the situation. Let's take a look at some slides from the lecture here. First, here's the demographic breakdown of Ukraine:
here's how the election in 2004 went:
this is the 2010 election:
As we can clearly see from the voting patterns in both elections, the country is divided exactly across the current line of conflict. Furthermore, a survey conducted in 2015 further shows that there is a sharp division between people of eastern and western Ukraine on which economic bloc they would rather belong to: