"There was such a firestorm," the member told CNBC. "You don't know what 's coming next, what he's going to say or do next."
In the face of corporate defections and the member's disclosure, Trump announced plans to dissolve the group and the Manufacturing Jobs Initiative council.
The strategic forum, led by Blackstone CEO Steve Schwarzman and made up of top business leaders, is separate from Trump's manufacturing council, which had seen seven defections this week.
The president and CEO of 3M, Inge Thulin, announced his resignation from the manufacturing council on Wednesday afternoon.
"I believe the initiative is no longer an effective vehicle for 3M to advance" its goals — to achieve a United States that is "stronger, healthier and more prosperous for all people," he said.
Seven of the White House councils' 37 members resigned this week, led by Merck CEO Kenneth Frazier's exit exit on Monday from the manufacturing council. Frazier left after Trump's waffling responses to the deadly right-wing violence in Charlottesville, Virginia over the weekend.
"As C.E.O. of Merck and as a matter of personal conscience, I feel a responsibility to take a stand against extremism," Frazier said.
Trump has attacked those who left the councils, tweeting at Frazier almost immediately after the Merck chief resigned and later tweeting, "For every CEO that drops out of the Manufacturing Council, I have many to take their place. Grandstanders should not have gone on. JOBS!"
Following Wednesday's decision by the advisory council to disband and condemn Trump's statements, the president said he would end both the Strategic and Policy Forum and the manufacturing council.
The business backlash to Trump follows his lukewarm response to violence at a white nationalist rally over the weekend, where one woman died and 19 people were injured after a car rammed into counterprotesters. On Tuesday, Trump appeared to equate torch-bearing white nationalists with the protesters who demonstrated against them.
"The thinking was it was important to do as a group," said the member of the advisory council. As a panel, not as individuals because it would have more significant impact. It makes a central point that it's not going to go forward. It's done."
The business leaders chose to dissolve the council in order to "condemn" the president's comments about the Charlottesville violence, the member said. The member described Trump's defiant press conference on Tuesday as a "tripwire."
They had heard from employees and customers about the advisory council.
"There really was nothing to debate," the member said.
The Strategic and Policy Forum, led by Schwarzman, featured:
Correction: The headline of this story has been updated to reflect that the Strategic and Policy Forum is separate from the manufacturing council that several business leaders left this week. It is the only council disbanding as of Wednesday afternoon.