“I did not award any $2 billion contract for procurement of weapons,” he said at a public event. “Where did the money come from… GEJ

Perhaps he didn’t award, but should have. Perhaps some other people did, but shouldn’t have. The good thing is that a long-overdue examination of Nigeria’s procurement malpractices may now find public expression.
If so, it must be a thorough and just exercise, and should include the military, security and intelligence communities spanning at least the past 10 – 15 years. The rot did not begin under President Jonathan, and while there is evidence that the NSA’s office gulped nearly $3bn between 2011 and 2015, Mr. Dasuki did not invent that office, and he did not arrive there until 2012.

The pursuit of Nigeria’s (recent) looters must be pursued on the basis of justice, not vengeance. That is why there was no need for the government to have advertised Mr. Dasuki last week as anything other than one of several suspects who should have been arrested and processed for trial together according to the law.
Instead, Mr. Dasuki was being figuratively “paraded” before the public and the press in the nauseating tradition of Nigeria’s criminal justice system where a suspect is brought before the press as though he has already been convicted. If the government is sure of its case, and of its anti-corruption claims—and if an underlying masterplan is not to deliberately lose a particular trial—the right place is before a judge under the nation’s laws.
Hopefully, the Buhari government understands it must demonstrate every case in court. Government spokesmen can say whatever they wish, but an official statement, no matter how eloquently it might be crafted, does not substitute for a carefully and competently-prepared prosecution.
Yes, looting Nigeria has been extremely easy for its practitioners, requiring ruthlessness rather than brains. Recovering those funds and putting the thieves in jail to rot away will take far more than simply identifying their wrongs.