Many people are divided on the issue of tax generally, especially on how the money generated is put to use, i don't have any problem with paying taxes, as long as the government uses the money correctly. Crypto taxes cannot be a way to console Nigerians, nobody likes some part of their money taken away from them, even when it is necessary. Crypto is taxed in the U.S. and in some other countries too, i guess Nigeria is next to impose tax on crypto, we'd see how it pans out.
They are not legalising anything, crypto itself isn't illegal in Nigeria, only be say government don ban banks from running package with crypto exchanges. The Nigerian government do not even have to legalize crypto to impose taxes on it, it is within their jurisdiction to do so without legalising Bitcoin.
Welcome brother.