Come 2021 we are in a Bull run again and crypto action is high in the country. The govt sends this letter to banks again to keep an eye out.
This is not a Ban on Bitcoin or cryptocurrency it is shutting down the onramps of fiat into crypto. There are also other nuanced issues in the country about the Central bank needing people to hold the currency (Naira) due to heavy devaluation going on at the moment but lots of people are converting all their money to BTC and this is a way to halt it.
Hope this clarifies this for some people