They have been buying energy out of necessity, I'll ask you, would it benefit Ukraine if the likes of Germany & France had no energy, tell me how that would help them aid Ukraine?
If you think about it, it makes less sense for Russia to sell to the EU than it does for the EU to buy from Russia. When you look at the figures, Ukraine gets about a 3 to 1 advantage. Basically Russia is paying for it's own destruction. If it wasn't for the fact that the Russian economy is on it's arse they would quit selling to the EU.