He is a dictator who controls money flowing in and out of country, using the tax revenue to fund his regime and wage war. He can't tax or block bitcoin payments, or steal proceeds by forcing foreign currency sale at a very unfair exchange rate.
Bitcoin helps live without paying taxes and fund opposition without repercussions. In fact, cryptocurrency payments are the only way for Russians to fund anti-Putin opposition. So anyone who says that cryptocurrencies are useless, please, kindly, stop saying this nonsense. If you are lucky to be born in a first world country you simply don't know how easily banking can be used to suffocate a person in a (lawless) cashless society. Bitcoin is a hedge against that, and a powerful one.