The good thing about baby steps
is that it does take a lot of the planning out of hands of "vision-free politicians" as you put it. Nasa's budget is fairly stable at around the $15 billion dollar mark. By doing things in an incremental approach, Nasa's director should be able to move the program along at a pace that is below the radar of most bureaucrats in Washington. That is assuming Nasa has a director which isn't a Washington bureaucrat himself.
By giving Congress one slice of the picture at a time, as opposed to the whole panoramic view, the chance of sticker shock scaring them away is greatly reduced. Feed the plan for space to them one bite at a time, instead of showing them the whole feast like Bush 41 did.