"If the Blagojevich thing had not been exposed now, the case might very well have gone undetected by the media."

Seriouslyb doubt that, Rig.   The bigger danger - and I think Fitzgerald wanted to avert this - was that Blago would go ahead and appoint someone to the Senate, which would then make the Senator appointee suspect.   That would have been a much bigger can of worms to have to deal with.   It certainly makes sense for Blagojevich to be busted before he did that much more damage.

As for the media, au contraire.   They'd have had a field day with a humongous, widespread political scancal that could be seen (spun) as threatening to bring down the Illinois governor, other Illinois politicians, the new Democratic administration, and perhaps the Democratic party as a whole.