It was alluded to in the post - contributors turn into maintainers. Someone who contributes has a small but plausible chance of sticking around.
For an open source project that isn't a business, that's really the only way to recruit people
But why recruit people, now that we have AI?
Couldn't an agent monitor feature requests and bug reports, reason about them, and then implement and fix the ones it deems important?
For the same reason software engineers still employed. AI is not yet capable of autonomous software development. From my perspective we're nowhere close.