There are various reasons Stallman couldn't make it as politician, but the most relevant one right now is that in the US we can't have candidates that can't be packaged like a product. Stallman is loud. He has long hair. He has mistakes on his record because he actually DID things. Worst, he doesn't believe the corporation should win in all circumstances, and that is a must for any candidate because ALL candidates, D or R, are pre-approved by corporations because of our out-of-control, free for all campaign financing.
You want someone good in government? You are not going to get anyone good in the government when they have to look like someone from a University’s stock photography collection. You aren't going to get a good person who hasn't smoked dope or maybe hasn't had a depressive episode or two. You need someone who has worked in some clothes other than suit or a business dress. You need someone real. And this is NOT happening in the US right now.