Richard Bullick was giving evidence to the Stormont inquiry into the sale of Nama's Northern Ireland portfolio.
Mr Bullick had a series of meetings with Frank Cushnahan and Ian Coulter between September 2013 and April 2014.
Mr Coulter was a leading solicitor, while Mr Cushnahan sat on Nama's Northern Ireland advisory committee.
It later emerged that both men could have got substantial payments as part of the £1bn deal.
Mr Cushnahan advised the Pimco fund after he left his Nama role and was in line to receive a £5m fee if its bid for the portfolio was successful, an Irish parliamentary committee was told.
The bid collapsed when Nama learned of Mr Cushnahan's role in March 2014.
The portfolio was eventually sold to the Cerberus fund in April 2014.
In the wake of that deal, Cerberus indirectly paid a fee of £7.5m to Tughans, the firm where Mr Coulter was managing partner.
A large portion of that money was then moved to an Isle of Man bank account under the control of Mr Coulter.
He said that transfer was for "a complex, commercially and legally-sensitive" reason. The money was later moved back and Mr Coulter left the firm.
Richard Bullick said his assumption was that any benefit for the men "would come from their clients getting freed up from Nama in the longer term".
"If there was greater economic activity, that would provide the opportunity for both Frank and Ian and their various businesses to do well," he said.
Mr Bullick said he was not aware of "the specific names" of any clients, and only assumed that some of them were in Nama.
He added that in his experience, Mr Cushnahan and Mr Coulter had "always acted in the best interests of Northern Ireland".
Mr Bullick said he did not have information to know if Mr Cushnahan had a conflict of interest in his Nama role.
The inquiry also questioned Sinn Féin adviser Dara O'Hagan, who worked for Deputy First Minister Martin McGuinness in the run up to the deal.
Mr McGuinness previously told the inquiry it was "totally, absolutely misleading" for the DUP to say he was being kept informed about the bid from Pimco.
He said First Minister Peter Robinson did at some point tell him Pimco had bid and subsequently withdrawn, but not the detail.
Ms O'Hagan was asked about an email sent to her concerning the possible terms of a deal under which Pimco would buy the portfolio.
She did not pass that email to Mr McGuinness.
She explained that was because Nama matters were primarily dealt with by the Department of Finance, and she expected it to produce a formal, detailed executive paper about the matter.
Ms O'Hagan said she would have brought it to Mr McGuinness at that stage.

Cryne joined Barnsley's board in 2003 as part of a consortium led by ex-Leeds chairman Peter Ridsdale.
Ridsdale left the Championship club in December 2004, leaving Cryne and former chairman Gordon Shepherd in control.
In August, Cryne told the Barnsley Chronicle that he would welcome takeover offers from fans' groups.
A DUP adviser who was "intensively involved" in the Nama loans sale process has said he never had "any understanding" that two businessmen stood to be paid as part of any deal.
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Barnsley owner Patrick Cryne will not be involved in the club "for the foreseeable future" while he receives cancer treatment.