And why would they do that? doesn't make sense at all.
If they would replace it, are there enough infrastructure in Afghanistan that will help them transact using BTC? First you have internet to be able to used bitcoin around that country, is there is none then it's useless.
Besides, do you think oppressive government like Taliban will allow the people to use crypto as way to hide their money and wealth? Or give financial freedom? Nah, don't think so.
Afghanistan needs infrastructure development and lots of it. Even in developed countries of the world like USA, EU not many are familiar with crypto. Moreover, governments all around the world are also showing strong opposition to crypto. I don't think that many governments will allow crypto to be used as official currency and Taliban's are not an exception.