Funny thing about corruption...It's very hard to quantify and as someone who spent couple of years living in China I would say there is no link between corruption and economic growth.
The corrupted politicians and people are only interested in enriching themselves at the expense of everything else. For them being a client state of either Russia or the EU makes no difference because they know that to reverse the course of the country it takes more than one generation and nobody has time for that especially when you are buying your next super yacht.