a replacement ready to go, but our head coach's actions to be fully publicized? Obviously there's a difference between the two, but the secrecy of both is critical to maintaining stability at ND. And in general your hypothetical world of Swarbrick striking hypothetical deals in principle with replacement coaches would require secrecy across the board in the industry.
It's entirely feasible for Kelly or his agent to A) explore NFL options and B) decide to stay at ND, last 5 more years, and win a National Championship. But publicizing A would all but rule out B, as recruits/players/coaches would look to jump ship.
Granted, B also may not be possible after A because I think Swarbrick suggested that Kelly better get the job if he ever dares look again. I'm kinda setting that aside, although it also suggests a need for some secrecy in Kelly's camp.