Sad to see this happening in Nigeria and its like that they are closing the doors of their citizens to learn something beneficial to them and it looks like their government doesn't want their citizens to improve their lives by discovering new technology which can possibly give them decent income. Anyways hopefully we can see a change of decision here since imposing a law like this is quite not good for people and its adoption.
Because a poor and vulnerable population is easy to control. They are scared that if people look for other ways of earning wealth away from their reach, then that would mean that they would not be able to control and manipulate the population.
It's a war the Nigerian Government will never win, the best thing they would try to do is maybe regulate crypto trading and maybe tax, but banning? Impossible.