I think it's because people are seeking ways to get out of the volatile currencies. Bitcoin blasted up relative to the Ruble today. It was up 40%+. Buyers are just trying to find a way to keep their money's value and keep from going completely broke. Investors are buying dollars, and crypto seems to be another option, to preserve value.
Once people have crypto they can sell it and converted it to any other currency so who knows if it will continue to go up but for now crypto seems to be working.
It's nuts. A few years ago few people thought that crypto would be used to escape a falling currency. It's happening now and people are having a hard time believing it.