Do you not understand how any of this works?? Hannity is dancing a jig right now! He’ll likely get that time slot back after Fox is done with guest hosts and, either way, will see a significant boost to his ratings. All of these hosts (most networks, but especially at Fox) are out for themselves and each commands a warring faction of producers and off-screen talent trying to outdo one another.
Edit: Also, it is extremely unlikely that Maddow leaves her cushy gig with NBC right now—she wields a lot of power behind the scenes and sets her own schedule. I don’t think she wants anything to do with a Murdoch-affiliated Fox…and her champion Roger Ailes is long gone.