To case maximum disruption in EU with rising gas prices. To avoid paying fines. To disrupt relations between Ukraine and Germany. There's many possible motivations.
> Lol, what could any country do if they don't pay the fines?
There's 300 billion dollars of russian money frozen on western accounts. International courts can allow Germany to take their money from there if Russia refuses to pay. Gasprom was clearly breeching the contract, and part of the contract is - which court can judge any disputes about it.
There's plenty of Ukrainians to choose from in Russia.