[croes]

Not to mention that Ukraine earned some billions in transit fees, which helped upgrading their military.

What if the EU had not bought Russian gas? Then Russia would probably have sold more to others like China or India and Ukraine would not have earned money from transit fees, nor would there be any leverage against Russia at all.

[chrischen]

Leverage would be more like buying Russian gas but having a backup. If you have no choice but to buy Russian gas then it is not leverage—in fact it is leverage against you.

Also If EU did not buy Russian gas and China and India were the only buyers then that lowers the price and profits Russia commands. In a liquid marketplace the number of buyers available contribute to profits.