NASA can only accomplish what they're authorized and funded to do
Unless I'm reading you wrong, it seems that you're falling for the mindset that NASA isn't just another government bureaucracy. In the end, that's all they are. NASA can only do what they're authorized and funded to do by Congress and the President. No more.
It doesn't matter if NASA wants to send people to Mars or do any other thing, it all comes down to funding authorizations. Like my favorite line from the movie, "The Right Stuff", "No bucks, no Buck Rogers."