And from which time traveler did you get this information?
The future is pretty hard to predict accurately, especially in such definitely terms like "never".
For instance, the Russians were cut off SWIFT. If the oligarchs had crypto, they could access their wealth and render sanctions ineffective.
Believe it or not the Ukrainians are in a war, and currency is not their biggest problem - that would be the tanks, and the bombs and the planes. Once the war resolves, so will their access to money. On the other hand, systems designed to evade sanctions are making that process longer and more painful - and more likely to resolve in the aggressors favor, as the Russians are better capitalized. The Russian people need to feel the pain to pressure their government to end the conflict.
Some pain is good, and so is our ability to inflict it.