why didn't President Obama visit "the giant of Africa"(Nigeria) during his visit to west africa

In what sense is Nigeria the Giant of Africa? During the campaign, the Nigerian Authority, almost took the election away from him by complicating the charge that he received donations from questionable sources, by going after okereke and her fellow unsolicited donors. The nigerian Authority must have taken him for granted because they know that in Nigeria, a man like him cannot win the election even when he wins the vote. And he did right by pointing out a country in decay.