I think they would have set him up to make him look foolish on stage to the point of walking off the stage... Here he controls the outcome. If it costs him vote fine. Don’t know why he’s meeting with O’Reilly other than to give O’Reilly the chance to tell him he’s wrong.
I would turn the interview around. Ask O’Reilly if he thought the press release and having plants there proper? Ask him if he honestly considered it to be a true debate.
Gives Trump a chance to express the basis for his decision, and Fox/O'Reilly a chance to defend the network. It shows that Trump is open to a "fair hearing," let the listeners decide. Plus, there are issues that dwarf the conduct of one debate. Trump can play up that a debate without him on the stage gives the other candidates more time and room to sell themselves to the public. He can be magnanimous about it.