I took a day to think about this. Trade is great but it is not enough.
Analogy: It is like saying that one of those bonding exercises that teams or couples do is the reason they are together. Sure those things help keep couples together, but they aren’t the reason for the union and once the reason is gone the union crumbles regardless of the exercises they do.
Trade didn’t stop the ’66 Igbo Pogroms, countless acts of mass ethnoreligious violence in the north and south, brexit (“in the abroad”) and it will not be the main reason Nigerians remain together.
Nations stay together either because of homogeneity or over-arching ideals. Nigeria needs the later (the former isn’t for us). Shared vision and purpose can form the foundation on which other things are built. Trade can then help solidify the process.
By the way the ideals we are running on now is oil money and convenience (past incidents have shown some that secession is costly).