"If the EU decides to support Ukraine then because of the devastating sanctions there is a strong chance Russia loses."
How did that not work then yet?
I would say because China and North Korea joined the train of gravy, to the point to NK selling food to Russian Army. Maybe India also helped to sustain the Russian economy for a while.
In any case Russia losing its oil refineries one by one is the real deal here.
They question you're really asking is "why is the war taking so long?"
Because it's a war.