That entirely fails to even mention the ethnic angle, which is probably the main thing never-mind the current political details. The western part of the country speaks Ukranian, not Russian, and was historically aligned with the Polish empire.
There isn't an ethnic angle - although Russian-speaking, the majority of the population of the east is also of Ukrainian ethnicity. Even the language thing isn't that big of a deal, almost all Ukrainians use both languages to some extent.
