I have heard interviews from a couple of people who think the Argos have been looking all along for someone from the US (re: NFL) and are close to getting Ryan Grigson who played for them briefly, started as a scout for the Riders and has been the GM of the Indy Colts. He would have made the decision on the coach and Milanovich saw the writing on the wall.
Michael Copeland did a great job as a league employee, so he didn't turn stupid over night, but what I think he did was under estimate the Toronto market and how badly is was neglected and dis-engaged the fan base was.
I think they want to make a big splash with a US guy with contacts to bring in guys who may not have normally came up here.
Or maybe I am completely wrong, who knows