>>It’s possible, but then how can we explain the previous victory of a pro-European west leader?<<
Pro-European sentiments has dominated at the time. The problem is that anti-Russian policies of that government has ruined Russian trade ties and affected economy really bad. It has shifted balance to a pro-Russian groups and led to Yanukovitz victory.
It seems to be the case that no matter who they elect, nobody can bring prosperity to both portions of Ukraine, and tackle the systemic low-level corruption that keeps small rural communities poor.