A lot of great open source comes out of startups because startups are really good at shipping fast and getting distribution (open source is part of this strategy). Users can try the tool immediately, and VC funding can put a lot of talent behind building something great very quickly.
The startup model absolutely creates incentive risk, but that’s true of any project that becomes important while depending on a relatively small set of maintainers or funders.
I’m not sure an acquisition is categorically different from a maintainer eventually moving on or burning out. In all of those cases, users who depend on the project take on some risk. That’s not unique to startups; it’s true of basically any software that becomes important.
There’s no perfect structure for open source here - public funding, nonprofit support, and startups all suck in their own ways.
And on the point you make about public funding being slow: yeah, talented people can’t work full-time on important things unless there’s serious funding behind it. uv got as good as it is because the funding let exceptional people work on it full-time with a level of intensity that public funding usually does not.