No one wants to elect a smug Twitter personality who's made his whole schtick about speaking for "SCIENCE" (despite not being a particularly accomplished scientist) and wearing ridiculous ties.
Also, if he made his platform all about going to Mars, reinvigorating NASA, reviving the Space Age, etc. that would probably flop hard. There are enough concrete problems on Earth for people to worry about. Even if he focused more on improving our science education and such, I just don't see him having broad appeal outside nerdy liberals who already unanimously vote D.
Even Bill Maher would probably do better and that's really saying something.
I maintain that the only liberal media personality who had really strong potential to be a formidable political candidate was Jon Stewart.
If Tyson were to run on a science platform he would be wise to have a strong climate change position that will be the main focus of his candidacy. Pushing for that and a strong vaccination during the pandemic would be a sure way to gain some support among the base. Would it be enough to overcome weakness remains the question mark, and you're right he just would not have a diverse base of voters to land on the path of nomination.
Jon Stewart would have been a very formidable candidate but Bill Maher would bomb much harder in the primary. If we think NDT is smug, Maher is the personification of it. Then you got the anti-religion views, his history of bigoted comments against multiple groups of people, pushing pseudoscience, he would be lucky to crack 2.5% in the primary.