My sense is that DHH is just a terrible boss.
Note the "changes" [1] are not just "no politics" but also "no more committees" (of any kind at all; that is, no authority or responsibility except individually along line-of-report hieararchy), no more 360 degree reviews (no way to formally give feedback to your boss), and no more bringing up past decisions you disagreed with (!). Basically, no more employee input in anything, and a new focus on "insubordination" (they're not using this word, but these policy changes are like -- do your job, don't tell us what your opinion is about anything else in the company especially if you don't like something).
They also introduced a 10% profit-sharing plan though, which could be real money?
I don't think the people leaving -- some of whom had been there for years -- are doing it for money. I think that's not usually why people leave a place, especially when leaving without another job lined up.
I don't think it's really about the "no politics at work" policy either.
I think it's probably mostly about not trusting or respecting or feeling respected by the boss.
[1] https://world.hey.com/jason/changes-at-basecamp-7f32afc5