I'm not too sure.
There have been some other really good (I think) biographical telemovies in a similar vein - "The Late Shift
" which showed the battle for the top late night talkshow spot between Leno and Letterman pending the stepping down of Carson (ironic to look at that now in light of what's going on with Leno and Fallon), who took the path of using relatively unknown actors and going out of their way to make them up to look a lot like the people they were portraying, as well as duplicate their mannerisms and speech patterns (they asked Rich Little to do a REALLY good Carson - something he was quite famous for at the time).
Then there was "Pirates of Silicon Valley
" that didn't quite concern themselves about making the actors look and act exactly like the people they were portraying, as much as trying to deliver an effective story with a higher level of general acting ability with a more well-known cast of players.
Both films had definite strengths, but took two very different paths concerning the talent they used to portray the key figures.