We Interrupt this Press Conference....
In NBC's case, at least, the network cut away from Bush's live speech to Brian Williams, who offered a summary of the presser while it was still actually happening, then to Tim Russert, who peddled his analysis of the presser while it was still actually happening, then to Andrea Mitchell, etc.
In other words, NBC didn't drop the president for Donald Trump. They dropped him so Williams, Mitchell, and Russert could get their mugs in the shot before "The Apprentice" started. If they had stayed with the conference till the very end, it still would have cut off the president by a minute or so, but at least another question or two would have gotten out to NBC viewers.
What kind of idiot decided that NBC's peanut-gallery-analysis of a live news event was more important than the live news event itself?