It's not just goods, Nigeria has a positive trade balance, normally that would mean more foreign currency enters the economy than is needed to ay for imports. The thing is that not only commerce matters but there is also a multitude of other factors, there are plenty of countries with a negative trade balance that are not having a problem keeping their currency up.
But the simple explanation is that there is more demand for $ than there is offer, so much for the so-called dedollarisation everyone prays for.
Seems like everyone hates the $ so much they want all of them stuffed in their pockets.
Yeah, that's the plan but doing it as you can see it's a lot harder than talking about it.