Things are both simple and complicated for case of Ukraine:
1) we (still) have different language preferences - a significant part of the country speaks russian. Some try to "migrate" to ukrainian but that is an endless source for (stupid) jokes. Nobody cared about language issues when people voted for independence of Ukraine in 1991. Majority understand well both languages and can speak both as well (basically VERY limited number of people speak "clean" ukrainian or russian without using words from the other language, sometimes transformed appropriately - just like kids do that)
2) we have different Christian confessions with issues like "we want our brand of Christianity with pagan gods included"; on the other hand - nobody cares about different kinds of Islam/Judaism, as well as Catholics, all sorts of cultists and so on.
3) some population wants to live in "Russia from TV" or maybe even real one but can't migrate there for obvious reasons (simply put - no money and bureaucracy). Some still dream of USSR - mostly retired people forced to live getting $100+-/month.
4) some will do anything for cash, sometimes after precalculating the final odds.

It's easy to spot multiple internal conflicts and things went well more or less till 2004 - with balance not being forced by either side. Winning presidential elections was a no-brainer - give some hints that you'll make 2 "state languages" and you get support from russian-speaking part, add something really valuable for ukrainian speakers - and you've got the majority. Then Maidan-2004 has happened, with typical "fight corruption" and "for everything good" promises, resulting in ignorance of votes of half of the country, a pause used for pouring a ton of sh*t on one candidate and praising the other and a third tour of voting; at the same time a part of the voters were mocked by another part - "Downbass" referring to Down syndrome and "Luganda" populated by "lugandonians" referring to Uganda (or Luanda - basically most people from the street will not tell the difference) and condoms, probably "condoniggaz" will be the suitable translation. And that parts of the country had all the coal mining and majority of heavy industry. Then hopes got broken by more corruption scandals directly related to the president and a clear win of the former looser in 2009. Of course even more corruption has followed (who'd have doubted) resulting in 2013 "Maidan" starting as usual and ending as totally radical nationalistic venue being carried out to all parts of the country; 2004 had a bit less nationalism and much less hatred, it was more a funny freak show.

Of course this situation was exploited by Russia - with full range grades of success (Crimea) and failures (Kharkiv, Dnipropetrovsk, Odesa) with Donbas region taking part somewhere in the middle. But who has created it and what were the goals? What did they expect or hoped for? Or they simply tried to pursue their own interests using third-party funds and doing what they were told to do? Maybe some day in memoirs we'll get the real picture.