Agreeing with your main point, i'll just point out that there were incipient protests in favor of the EU in the East, but 1) it's really easy to quench a local action unsupported by the body of the protest, after which sane people would either shut up or join the main force, 2) the capital, built upon the Dnieper River, is hardly in the west, 3) there were anti-EU protests in Kyiv, which is partly why there was street-fighting (I mean, beside the Berkut).

And polarization had been present before December '14, but it skyrocketed after.